How to trim whitespace from a Bash variable

Question

I have a shell script with this code   var  hg st -R   path   if   -n   var     then     echo  var fi   But the conditional code always executes  because hg st always prints at least one newline character    Is there a simple way to strip whitespace from  var  like trim   in PHP     or   Is there a standard way of dealing with this issue    I could use sed or AWK  but I d like to think there is a more elegant solution to this problem

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Execute this script with the string argument passed in double quotes      var2 gives the string without spaces    1 is the string passed in double quotes    bin bash var2  echo  1   sed  s      g   echo  var2

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Python has a function strip   that works identically to PHP s trim    so we can just do a little inline Python to make an easily understandable utility for this   alias trim  python -c  import sys  sys stdout write sys stdin read   strip        This will trim leading and trailing whitespace  including newlines      x  echo -e   n t    n    trim    if   -z   x     then echo hi  fi hi

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I found that I needed to add some code from a messy sdiff output in order to clean it up   sdiff -s column1 txt column2 txt   grep -F   lt     cut -f1 -d  lt    gt  c12diff txt  sed -n 1 p  c12diff txt   sed  s      g    tr -d   n    tr -d   t    This removes the trailing spaces and other invisible characters

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I created the following functions  I am not sure how portable printf is  but the beauty of this solution is you can specify exactly what is  white space  by adding more character codes       iswhitespace                 n  printf   d n     1            if     n     13      amp  amp      n     10      amp  amp      n     32      amp  amp      n     92      amp  amp      n     110      amp  amp      n     114      then             return 0         fi         return 1            trim                 i 0         str   1          while    i  lt     1             do             char   1  i 1              iswhitespace   char              if        -eq  0     then                 str    str  i                   i    1              fi                i    1            done         i    str          while    i  gt   0             do                i -  1                char   str  i 1              iswhitespace   char              if        -eq  0     then                    i    1                    str    str 0  i                   i 0             fi         done         echo   str          Call it like so mystring  trim   mystring

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Let s define a variable containing leading  trailing  and intermediate whitespace   FOO   test test test   echo -e  FOO    FOO       gt  FOO   test test test   echo -e  length FOO      FOO      gt  length FOO   16     How to remove all whitespace  denoted by   space   in tr    FOO   test test test   FOO NO WHITESPACE    echo -e    FOO     tr -d    space      echo -e  FOO NO WHITESPACE    FOO NO WHITESPACE       gt  FOO NO WHITESPACE  testtesttest  echo -e  length FOO NO WHITESPACE      FOO NO WHITESPACE      gt  length FOO NO WHITESPACE   12     How to remove leading whitespace only   FOO   test test test   FOO NO LEAD SPACE    echo -e    FOO     sed -e  s     space          echo -e  FOO NO LEAD SPACE    FOO NO LEAD SPACE       gt  FOO NO LEAD SPACE  test test test   echo -e  length FOO NO LEAD SPACE      FOO NO LEAD SPACE      gt  length FOO NO LEAD SPACE   15     How to remove trailing whitespace only   FOO   test test test   FOO NO TRAIL SPACE    echo -e    FOO     sed -e  s    space           echo -e  FOO NO TRAIL SPACE    FOO NO TRAIL SPACE       gt  FOO NO TRAIL SPACE   test test test  echo -e  length FOO NO TRAIL SPACE      FOO NO TRAIL SPACE      gt  length FOO NO TRAIL SPACE   15     How to remove both leading and trailing spaces--chain the seds   FOO   test test test   FOO NO EXTERNAL SPACE    echo -e    FOO     sed -e  s     space        -e  s    space           echo -e  FOO NO EXTERNAL SPACE    FOO NO EXTERNAL SPACE       gt  FOO NO EXTERNAL SPACE  test test test  echo -e  length FOO NO EXTERNAL SPACE      FOO NO EXTERNAL SPACE      gt  length FOO NO EXTERNAL SPACE   14   Alternatively  if your bash supports it  you can replace echo -e    FOO     sed     with sed      lt  lt  lt   FOO   like so  for trailing whitespace    FOO NO TRAIL SPACE    sed -e  s    space          lt  lt  lt   FOO

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Here s a trim   function that trims and normalizes whitespace     bin bash function trim       echo       echo     trim    one   two    three          one two three    And another variant that uses regular expressions      bin bash function trim       local trimmed          if      trimmed                               then          trimmed   BASH REMATCH 1       fi     echo   trimmed     echo     trim    one   two    three          one   two    three

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I would simply use sed   function trim       echo   1    sed -n  1h 1 H    g s     t    g s    t     g p        a  Example of usage on single-line string  string      wordA wordB  wordC   wordD      trimmed    trim   string     echo  GIVEN STRING    string   echo  TRIMMED STRING    trimmed     Output   GIVEN STRING       wordA wordB  wordC   wordD      TRIMMED STRING   wordA wordB  wordC   wordD    b  Example of usage on multi-line string  string      wordA     gt wordB lt  wordC      trimmed    trim   string     echo -e  GIVEN STRING    string  n  echo  TRIMMED STRING    trimmed     Output   GIVEN STRING       wordAA     gt wordB lt  wordC       TRIMMED STRING   wordAA     gt wordB lt  wordC    c  Final note  If you don t like to use a function  for single-line string you can simply use a  easier to remember  command like   echo   string    sed -e  s     t        sed -e  s    t         Example   echo     wordA wordB wordC       sed -e  s     t        sed -e  s    t         Output   wordA wordB wordC   Using the above on multi-line strings will work as well  but please note that it will cut any trailing leading internal multiple space as well  as GuruM noticed in the comments  string      wordAA      gt four spaces before lt    gt one space before lt       echo   string    sed -e  s     t        sed -e  s    t         Output   wordAA  gt four spaces before lt   gt one space before lt    So if you do mind to keep those spaces  please use the function at the beginning of my answer   d  EXPLANATION of the sed syntax  find and replace  on multi-line strings used inside the function trim   sed -n     If the first line  copy the pattern to the hold buffer 1h   If not the first line  then append the pattern to the hold buffer 1 H   If the last line then               Copy from the hold to the pattern buffer     g       Do the search and replace     s     t    g     s    t     g       print     p

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To remove spaces and tabs from left to first word  enter   echo       This is a test    sed  s     t        cyberciti biz tips delete-leading-spaces-from-front-of-each-word html

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I ve seen scripts just use variable assignment to do the job     xyz  echo -e  foo  n bar     echo  xyz foo bar   Whitespace is automatically coalesced and trimmed   One has to be careful of shell metacharacters  potential injection risk    I would also recommend always double-quoting variable substitutions in shell conditionals   if   -n   var     then   since something like a -o or other content in the variable could amend your test arguments

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This does not have the problem with unwanted globbing  also  interior white-space is unmodified  assuming that  IFS is set to the default  which is    t n     It reads up to the first newline  and doesn t include it  or the end of string  whichever comes first  and strips away any mix of leading and trailing space and  t characters  If you want to preserve multiple lines  and also strip leading and trailing newlines   use read -r -d    var  lt  lt  eof instead  note  however  that if your input happens to contain  neof  it will be cut off just before   Other forms of white space  namely  r   f  and  v  are not stripped  even if you add them to  IFS    read -r var  lt  lt  eof  var eof

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Let s define a variable containing leading  trailing  and intermediate whitespace   FOO   test test test   echo -e  FOO    FOO       gt  FOO   test test test   echo -e  length FOO      FOO      gt  length FOO   16     How to remove all whitespace  denoted by   space   in tr    FOO   test test test   FOO NO WHITESPACE    echo -e    FOO     tr -d    space      echo -e  FOO NO WHITESPACE    FOO NO WHITESPACE       gt  FOO NO WHITESPACE  testtesttest  echo -e  length FOO NO WHITESPACE      FOO NO WHITESPACE      gt  length FOO NO WHITESPACE   12     How to remove leading whitespace only   FOO   test test test   FOO NO LEAD SPACE    echo -e    FOO     sed -e  s     space          echo -e  FOO NO LEAD SPACE    FOO NO LEAD SPACE       gt  FOO NO LEAD SPACE  test test test   echo -e  length FOO NO LEAD SPACE      FOO NO LEAD SPACE      gt  length FOO NO LEAD SPACE   15     How to remove trailing whitespace only   FOO   test test test   FOO NO TRAIL SPACE    echo -e    FOO     sed -e  s    space           echo -e  FOO NO TRAIL SPACE    FOO NO TRAIL SPACE       gt  FOO NO TRAIL SPACE   test test test  echo -e  length FOO NO TRAIL SPACE      FOO NO TRAIL SPACE      gt  length FOO NO TRAIL SPACE   15     How to remove both leading and trailing spaces--chain the seds   FOO   test test test   FOO NO EXTERNAL SPACE    echo -e    FOO     sed -e  s     space        -e  s    space           echo -e  FOO NO EXTERNAL SPACE    FOO NO EXTERNAL SPACE       gt  FOO NO EXTERNAL SPACE  test test test  echo -e  length FOO NO EXTERNAL SPACE      FOO NO EXTERNAL SPACE      gt  length FOO NO EXTERNAL SPACE   14   Alternatively  if your bash supports it  you can replace echo -e    FOO     sed     with sed      lt  lt  lt   FOO   like so  for trailing whitespace    FOO NO TRAIL SPACE    sed -e  s    space          lt  lt  lt   FOO

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I needed to trim whitespace from a script when the IFS variable was set to something else  Relying on Perl did the trick     trim     echo  1      This doesn t seem to work  as it s affected by IFS  trim     echo   1    perl -p -e  s   s   s    g      strings  after -- gt     lt -- before    lt -- both -- gt      OLD IFS  IFS IFS     for str in   strings   do   str   trim    str      echo  str     str    done IFS  OLD IFS

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There are a lot of answers  but I still believe my just-written script is worth being mentioned because    it was successfully tested in the shells bash dash busybox shell it is extremely small it doesn t depend on external commands and doesn t need to fork  - fast and low resource usage  it works as expected    it strips all spaces and tabs from beginning and end  but not more important  it doesn t remove anything from the middle of the string  many other answers do   even newlines will remain special  the      joins multiple arguments using one space  if you want to trim  amp  output only the first argument  use   1  instead if doesn t have any problems with matching file name patterns etc    The script   trim       local s2 s        until s2    s    space           s2      s     do s   s2   done   until s2    s    space           s2      s     do s   s2   done   echo   s      Usage   mystring     here     is     something      mystring   trim   mystring   echo   gt  mystring lt     Output    gt here     is     something lt

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Use AWK   echo  var   awk   gsub               1

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You can delete newlines with tr   var  hg st -R   path    tr -d   n   if   -n  var    then     echo  var done

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Strip leading and trailing white space  new line inclusive   trim             1         space          space             printf   s    BASH REMATCH      OR    Strip leading white space  new line inclusive   ltrim             1         space             printf   s    BASH REMATCH       Strip trailing white space  new line inclusive   rtrim             1           space           printf   s    BASH REMATCH       Strip leading and trailing white space  new line inclusive   trim        printf   s     rtrim    ltrim   1          OR    Strip leading and trailing specified characters   ex  str   trim   str     n a   trim        if     2     then         trim chrs   2      else         trim chrs    space        fi           1         trim chrs          trim chrs      trim chrs            printf   s     BASH REMATCH 1        OR     Strip leading specified characters   ex  str   ltrim   str     n a   ltrim        if     2     then         trim chrs   2      else         trim chrs    space        fi           1         trim chrs          trim chrs           printf   s     BASH REMATCH 1         Strip trailing specified characters   ex  str   rtrim   str     n a   rtrim        if     2     then         trim chrs   2      else         trim chrs    space        fi           1             trim chrs      trim chrs            printf   s     BASH REMATCH 1         Strip leading and trailing specified characters   ex  str   trim   str     n a   trim        printf   s     rtrim    ltrim   1    2      2        OR  Building upon moskit s expr soulution       Strip leading and trailing white space  new line inclusive   trim        printf   s    expr   1         space            space        space             OR    Strip leading white space  new line inclusive   ltrim        printf   s    expr   1         space            space              Strip trailing white space  new line inclusive   rtrim        printf   s    expr   1              space        space              Strip leading and trailing white space  new line inclusive   trim        printf   s     rtrim    ltrim   1

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You can delete newlines with tr   var  hg st -R   path    tr -d   n   if   -n  var    then     echo  var done

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Strip leading and trailing white space  new line inclusive   trim             1         space          space             printf   s    BASH REMATCH      OR    Strip leading white space  new line inclusive   ltrim             1         space             printf   s    BASH REMATCH       Strip trailing white space  new line inclusive   rtrim             1           space           printf   s    BASH REMATCH       Strip leading and trailing white space  new line inclusive   trim        printf   s     rtrim    ltrim   1          OR    Strip leading and trailing specified characters   ex  str   trim   str     n a   trim        if     2     then         trim chrs   2      else         trim chrs    space        fi           1         trim chrs          trim chrs      trim chrs            printf   s     BASH REMATCH 1        OR     Strip leading specified characters   ex  str   ltrim   str     n a   ltrim        if     2     then         trim chrs   2      else         trim chrs    space        fi           1         trim chrs          trim chrs           printf   s     BASH REMATCH 1         Strip trailing specified characters   ex  str   rtrim   str     n a   rtrim        if     2     then         trim chrs   2      else         trim chrs    space        fi           1             trim chrs      trim chrs            printf   s     BASH REMATCH 1         Strip leading and trailing specified characters   ex  str   trim   str     n a   trim        printf   s     rtrim    ltrim   1    2      2        OR  Building upon moskit s expr soulution       Strip leading and trailing white space  new line inclusive   trim        printf   s    expr   1         space            space        space             OR    Strip leading white space  new line inclusive   ltrim        printf   s    expr   1         space            space              Strip trailing white space  new line inclusive   rtrim        printf   s    expr   1              space        space              Strip leading and trailing white space  new line inclusive   trim        printf   s     rtrim    ltrim   1

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Use this simple Bash parameter expansion     x   a z     e r ty     echo  START   x      END  START azerty END

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Yet another solution with unit tests which trims  IFS from stdin  and works with any input separator  even    0     ltrim           Left-trim  IFS from stdin as a single line        1  Line separator  default NUL      local trimmed     while IFS  read -r -d    1-   -u 9     do         if   -n    trimmed defined             then             printf  s   REPLY          else             printf  s    REPLY    REPLY     IFS               fi         printf    1- x00           trimmed true     done 9 lt  amp 0      if     REPLY        then           No delimiter at last line         if   -n    trimmed defined             then             printf  s   REPLY          else             printf  s    REPLY    REPLY     IFS               fi     fi    rtrim           Right-trim  IFS from stdin as a single line        1  Line separator  default NUL      local previous last     while IFS  read -r -d    1-   -u 9     do         if   -n    previous defined             then             printf  s   previous              printf    1- x00           fi         previous   REPLY      done 9 lt  amp 0      if     REPLY        then           No delimiter at last line         last   REPLY          printf  s   previous          if   -n    previous defined             then             printf    1- x00           fi     else         last   previous      fi      right whitespace    last      IFS        printf  s    last  right whitespace      trim           Trim  IFS from individual lines        1  Line separator  default NUL      ltrim   1         rtrim   1

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bin bash  function trim       typeset trimVar     eval trimVar      1       read trimVar  lt  lt  EOTtrim      trimVar EOTtrim     eval  1   trimVar      Note that the parameter to the function is the NAME of the variable to trim     not the variable contents   However  the contents are trimmed      Example of use  while read aLine do     trim aline     echo     aline    done  lt  info txt      File info txt contents    ------------------------------   ok  hello there           another  line   here        and yet another        only at the front          Output    ok  hello there    another  line   here    and yet another    only at the front

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Use   trim         local orig   1      local trmd        while true      do         trmd    orig    space              trmd    trmd    space              test   trmd      orig   amp  amp  break         orig   trmd      done     printf --   s n    trmd       It works on all kinds of whitespace  including newline  It does not need to modify shopt  It preserves inside whitespace  including newline    Unit test  for manual review       bin bash    trim sh  enum         echo     a b c      echo  a b c         echo    a b c       echo   a b c        echo   a  b c        echo   a  b  c        echo   a      b  c        echo       a      b  c        echo       a  b  c        echo   a  b  c            echo   a  b  c            echo   a N b  c        echo  N a N b  c        echo   Na  b  c        echo   a  b  c N       echo   a  b  c  N     xcheck         local testln result     while IFS    read testln      do         testln   tr N   n   lt  lt  lt   testln           echo                                  gt  amp 2         result    trim   testln            echo  testln   testln    gt  amp 2         echo  result   result    gt  amp 2     done    enum   xcheck

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You can delete newlines with tr   var  hg st -R   path    tr -d   n   if   -n  var    then     echo  var done

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This will remove all the whitespaces from your String     VAR2    VAR2     space           replaces the first occurrence and    all occurrences of whitespaces in the string  I e  all white spaces get replaced by     nothing

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From Bash Guide section on globbing    To use an extglob in a parameter expansion      Turn on extended globbing   shopt -s extglob     Trim leading and trailing whitespace from a variable   x   x       space       x   x       space          Turn off extended globbing   shopt -u extglob     Here s the same functionality wrapped in a function  NOTE  Need to quote input string passed to function    trim           Determine if  extglob  is currently on      local extglobWasOff 1     shopt extglob  gt  dev null  amp  amp  extglobWasOff 0         extglobWasOff     amp  amp  shopt -s extglob   Turn  extglob  on  if currently turned off        Trim leading and trailing whitespace     local var  1     var   var       space          var   var       space             extglobWasOff     amp  amp  shopt -u extglob   If  extglob  was off before  turn it back off      echo -n   var     Output trimmed string      Usage   string     abc def ghi      need to quote input-string to preserve internal white-space if any trimmed   trim   string      echo   trimmed       If we alter the function to execute in a subshell  we don t have to worry about examining the current shell option for extglob  we can just set it without affecting the current shell  This simplifies the function tremendously  I also update the positional parameters  in place  so I don t even need a local variable  trim         shopt -s extglob     set --    1       space           printf   s     1       space            so     s    t n  r tfoo      shopt -u extglob   shopt extglob extglob         off   printf   gt  q lt  n    s     trim   s     gt    t n  r tfoo    lt   gt foo lt    shopt extglob extglob         off

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I found that I needed to add some code from a messy sdiff output in order to clean it up   sdiff -s column1 txt column2 txt   grep -F   lt     cut -f1 -d  lt    gt  c12diff txt  sed -n 1 p  c12diff txt   sed  s      g    tr -d   n    tr -d   t    This removes the trailing spaces and other invisible characters

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Use   var  expr   var                            It removes leading and trailing spaces and is the most basic solution  I believe  Not Bash built-in  but  expr  is a part of coreutils  so at least no standalone utilities are needed like sed or AWK

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bin bash  function trim       typeset trimVar     eval trimVar      1       read trimVar  lt  lt  EOTtrim      trimVar EOTtrim     eval  1   trimVar      Note that the parameter to the function is the NAME of the variable to trim     not the variable contents   However  the contents are trimmed      Example of use  while read aLine do     trim aline     echo     aline    done  lt  info txt      File info txt contents    ------------------------------   ok  hello there           another  line   here        and yet another        only at the front          Output    ok  hello there    another  line   here    and yet another    only at the front

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You can trim simply with echo   foo   qsdqsd qsdqs q qs        Not trimmed echo    foo      Trim foo  echo  foo     Trimmed echo    foo

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You can delete newlines with tr   var  hg st -R   path    tr -d   n   if   -n  var    then     echo  var done

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This is the simplest method I ve seen   It only uses Bash  it s only a few lines  the regexp is simple  and it matches all forms of whitespace   if      test         space         space         space       space         then      test   BASH REMATCH 1   fi   Here is a sample script to test it with   test   echo -e   n  t Spaces and tabs and newlines be gone   t   n     echo  Let s see if this works   echo echo  ----------  echo -e  Testing   test   Tested     Ugh  echo  ----------  echo echo  Ugh   Let s fix that      if      test         space         space         space       space         then      test   BASH REMATCH 1   fi  echo echo  ----------  echo -e  Testing   test  Tested      Testing Spaces and tabs and newlines be gone   echo  ----------  echo echo  Ah  much better

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I created the following functions  I am not sure how portable printf is  but the beauty of this solution is you can specify exactly what is  white space  by adding more character codes       iswhitespace                 n  printf   d n     1            if     n     13      amp  amp      n     10      amp  amp      n     32      amp  amp      n     92      amp  amp      n     110      amp  amp      n     114      then             return 0         fi         return 1            trim                 i 0         str   1          while    i  lt     1             do             char   1  i 1              iswhitespace   char              if        -eq  0     then                 str    str  i                   i    1              fi                i    1            done         i    str          while    i  gt   0             do                i -  1                char   str  i 1              iswhitespace   char              if        -eq  0     then                    i    1                    str    str 0  i                   i 0             fi         done         echo   str          Call it like so mystring  trim   mystring

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Removing spaces to one space    text    fmt -su

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Bash has a feature called parameter expansion  which  among other things  allows string replacement based on so-called patterns  patterns resemble regular expressions  but there are fundamental differences and limitations    flussence s original line  Bash has regular expressions  but they re well-hidden    The following demonstrates how to remove all white space  even from the interior  from a variable value      var  abc def    echo   var  abc def   Note  flussence s original expression was    var       which only replaced the  first  space char   wherever it appeared    echo -n    var     space       abcdef

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Bash has a feature called parameter expansion  which  among other things  allows string replacement based on so-called patterns  patterns resemble regular expressions  but there are fundamental differences and limitations    flussence s original line  Bash has regular expressions  but they re well-hidden    The following demonstrates how to remove all white space  even from the interior  from a variable value      var  abc def    echo   var  abc def   Note  flussence s original expression was    var       which only replaced the  first  space char   wherever it appeared    echo -n    var     space       abcdef

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A simple answer is   echo     lol      xargs   Xargs will do the trimming for you  It s one command program  no parameters  returns the trimmed string  easy as that   Note  this doesn t remove all internal spaces so  foo bar  stays the same  it does NOT become  foobar   However  multiple spaces will be condensed to single spaces  so  foo    bar  will become  foo bar   In addition it doesn t remove end of lines characters

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There is a solution which only uses Bash built-ins called wildcards   var      abc        remove leading whitespace characters var    var    var      space           remove trailing whitespace characters var    var    var       space           printf   s       var       Here s the same wrapped in a function   trim         local var            remove leading whitespace characters     var    var    var      space               remove trailing whitespace characters     var    var    var       space               printf   s    var      You pass the string to be trimmed in quoted form  e g     trim     abc       A nice thing about this solution is that it will work with any POSIX-compliant shell   Reference   Remove leading  amp  trailing whitespace from a Bash variable  original source

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I needed to trim whitespace from a script when the IFS variable was set to something else  Relying on Perl did the trick     trim     echo  1      This doesn t seem to work  as it s affected by IFS  trim     echo   1    perl -p -e  s   s   s    g      strings  after -- gt     lt -- before    lt -- both -- gt      OLD IFS  IFS IFS     for str in   strings   do   str   trim    str      echo  str     str    done IFS  OLD IFS

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You can use old-school tr  For example  this returns the number of modified files in a git repository  whitespaces stripped   MYVAR  git ls-files -m wc -l tr -d

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Here s a trim   function that trims and normalizes whitespace     bin bash function trim       echo       echo     trim    one   two    three          one two three    And another variant that uses regular expressions      bin bash function trim       local trimmed          if      trimmed                               then          trimmed   BASH REMATCH 1       fi     echo   trimmed     echo     trim    one   two    three          one   two    three

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Use   var  expr   var                            It removes leading and trailing spaces and is the most basic solution  I believe  Not Bash built-in  but  expr  is a part of coreutils  so at least no standalone utilities are needed like sed or AWK

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Strip one leading and one trailing space  trim         local trimmed   1         Strip leading space      trimmed    trimmed            Strip trailing space      trimmed    trimmed           echo   trimmed      For example   test1    trim   one leading    test2    trim  one trailing     test3    trim   one leading and one trailing     echo    test1     test2     test3     Output    one leading    one trailing    one leading and one trailing    Strip all leading and trailing spaces  trim         local trimmed   1         Strip leading spaces      while     trimmed             do        trimmed    trimmed          done       Strip trailing spaces      while     trimmed             do         trimmed    trimmed          done      echo   trimmed      For example   test4    trim    two leading    test5    trim  two trailing      test6    trim    two leading and two trailing      echo    test4     test5     test6     Output    two leading    two trailing    two leading and two trailing

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While it s not strictly Bash this will do what you want and more   php -r   x   trim    hi there      echo  x     If you want to make it lowercase too  do   php -r   x   trim    Hi There       x   strtolower  x    echo  x

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This is the simplest method I ve seen   It only uses Bash  it s only a few lines  the regexp is simple  and it matches all forms of whitespace   if      test         space         space         space       space         then      test   BASH REMATCH 1   fi   Here is a sample script to test it with   test   echo -e   n  t Spaces and tabs and newlines be gone   t   n     echo  Let s see if this works   echo echo  ----------  echo -e  Testing   test   Tested     Ugh  echo  ----------  echo echo  Ugh   Let s fix that      if      test         space         space         space       space         then      test   BASH REMATCH 1   fi  echo echo  ----------  echo -e  Testing   test  Tested      Testing Spaces and tabs and newlines be gone   echo  ----------  echo echo  Ah  much better

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var     a b c     trimmed   echo  var

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With Bash s extended pattern matching features enabled  shopt -s extglob   you can use this    trimmed         to remove an arbitrary amount of leading spaces

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trim   removes whitespaces  and tabs  non-printable characters  I am considering just whitespaces for simplicity   My version of a solution   var    hg st -R   path      I often like to enclose shell output in double quotes var    echo    var     sed  s                g      This is my suggestion if   -n   var     then  echo     var    fi   The  sed  command trims only leading and trailing whitespaces  but it can be piped to the first command as well resulting in   var    hg st -R   path    sed  s                g    if   -n   var     then  echo     var    fi

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I ve seen scripts just use variable assignment to do the job     xyz  echo -e  foo  n bar     echo  xyz foo bar   Whitespace is automatically coalesced and trimmed   One has to be careful of shell metacharacters  potential injection risk    I would also recommend always double-quoting variable substitutions in shell conditionals   if   -n   var     then   since something like a -o or other content in the variable could amend your test arguments

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I ve always done it with sed    var  hg st -R   path    sed -e  s            If there is a more elegant solution  I hope somebody posts it

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Use this simple Bash parameter expansion     x   a z     e r ty     echo  START   x      END  START azerty END

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Assignments ignore leading and trailing whitespace and as such can be used to trim     var  echo     hello    echo  var hello

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Bash has a feature called parameter expansion  which  among other things  allows string replacement based on so-called patterns  patterns resemble regular expressions  but there are fundamental differences and limitations    flussence s original line  Bash has regular expressions  but they re well-hidden    The following demonstrates how to remove all white space  even from the interior  from a variable value      var  abc def    echo   var  abc def   Note  flussence s original expression was    var       which only replaced the  first  space char   wherever it appeared    echo -n    var     space       abcdef

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I had to test the result  numeric  from a command but it seemed the variable with the result was containing spaces and some non printable characters  Therefore even after a  trim  the comparison was erroneous  I solved it by extracting the numerical part from the variable   numerical var   echo   var with result from command    grep -o   0-9

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In order to remove all the spaces from the beginning and the end of a string  including end of line characters    echo  variable   xargs echo -n   This will remove duplicate spaces also   echo    this string has a lot       of spaces     xargs echo -n   Produces   this string has a lot of spaces

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From Bash Guide section on globbing    To use an extglob in a parameter expansion      Turn on extended globbing   shopt -s extglob     Trim leading and trailing whitespace from a variable   x   x       space       x   x       space          Turn off extended globbing   shopt -u extglob     Here s the same functionality wrapped in a function  NOTE  Need to quote input string passed to function    trim           Determine if  extglob  is currently on      local extglobWasOff 1     shopt extglob  gt  dev null  amp  amp  extglobWasOff 0         extglobWasOff     amp  amp  shopt -s extglob   Turn  extglob  on  if currently turned off        Trim leading and trailing whitespace     local var  1     var   var       space          var   var       space             extglobWasOff     amp  amp  shopt -u extglob   If  extglob  was off before  turn it back off      echo -n   var     Output trimmed string      Usage   string     abc def ghi      need to quote input-string to preserve internal white-space if any trimmed   trim   string      echo   trimmed       If we alter the function to execute in a subshell  we don t have to worry about examining the current shell option for extglob  we can just set it without affecting the current shell  This simplifies the function tremendously  I also update the positional parameters  in place  so I don t even need a local variable  trim         shopt -s extglob     set --    1       space           printf   s     1       space            so     s    t n  r tfoo      shopt -u extglob   shopt extglob extglob         off   printf   gt  q lt  n    s     trim   s     gt    t n  r tfoo    lt   gt foo lt    shopt extglob extglob         off

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Strip one leading and one trailing space  trim         local trimmed   1         Strip leading space      trimmed    trimmed            Strip trailing space      trimmed    trimmed           echo   trimmed      For example   test1    trim   one leading    test2    trim  one trailing     test3    trim   one leading and one trailing     echo    test1     test2     test3     Output    one leading    one trailing    one leading and one trailing    Strip all leading and trailing spaces  trim         local trimmed   1         Strip leading spaces      while     trimmed             do        trimmed    trimmed          done       Strip trailing spaces      while     trimmed             do         trimmed    trimmed          done      echo   trimmed      For example   test4    trim    two leading    test5    trim  two trailing      test6    trim    two leading and two trailing      echo    test4     test5     test6     Output    two leading    two trailing    two leading and two trailing

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Use   trim         local orig   1      local trmd        while true      do         trmd    orig    space              trmd    trmd    space              test   trmd      orig   amp  amp  break         orig   trmd      done     printf --   s n    trmd       It works on all kinds of whitespace  including newline  It does not need to modify shopt  It preserves inside whitespace  including newline    Unit test  for manual review       bin bash    trim sh  enum         echo     a b c      echo  a b c         echo    a b c       echo   a b c        echo   a  b c        echo   a  b  c        echo   a      b  c        echo       a      b  c        echo       a  b  c        echo   a  b  c            echo   a  b  c            echo   a N b  c        echo  N a N b  c        echo   Na  b  c        echo   a  b  c N       echo   a  b  c  N     xcheck         local testln result     while IFS    read testln      do         testln   tr N   n   lt  lt  lt   testln           echo                                  gt  amp 2         result    trim   testln            echo  testln   testln    gt  amp 2         echo  result   result    gt  amp 2     done    enum   xcheck

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var    a b    echo    set -f  echo  var     gt a b

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I ve seen scripts just use variable assignment to do the job     xyz  echo -e  foo  n bar     echo  xyz foo bar   Whitespace is automatically coalesced and trimmed   One has to be careful of shell metacharacters  potential injection risk    I would also recommend always double-quoting variable substitutions in shell conditionals   if   -n   var     then   since something like a -o or other content in the variable could amend your test arguments

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You can trim simply with echo   foo   qsdqsd qsdqs q qs        Not trimmed echo    foo      Trim foo  echo  foo     Trimmed echo    foo

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This trims multiple spaces of the front and end  whatever   whatever       whatever   whatever

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Execute this script with the string argument passed in double quotes      var2 gives the string without spaces    1 is the string passed in double quotes    bin bash var2  echo  1   sed  s      g   echo  var2

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Trim whitespace from both ends of specified parameter  trim          read -rd     1  lt  lt  lt     1        Unit test for trim    test trim          local foo   1      trim foo     test   foo      2     test trim hey hey  amp  amp  test trim    hey  hey  amp  amp  test trim  ho    ho  amp  amp  test trim  hey ho   hey ho   amp  amp  test trim    hey  ho     hey  ho   amp  amp  test trim    n n t hey n t ho  t n    hey n t ho   amp  amp  test trim    n      amp  amp  test trim   n    n   amp  amp  echo passed

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Bash has a feature called parameter expansion  which  among other things  allows string replacement based on so-called patterns  patterns resemble regular expressions  but there are fundamental differences and limitations    flussence s original line  Bash has regular expressions  but they re well-hidden    The following demonstrates how to remove all white space  even from the interior  from a variable value      var  abc def    echo   var  abc def   Note  flussence s original expression was    var       which only replaced the  first  space char   wherever it appeared    echo -n    var     space       abcdef

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I ve seen scripts just use variable assignment to do the job     xyz  echo -e  foo  n bar     echo  xyz foo bar   Whitespace is automatically coalesced and trimmed   One has to be careful of shell metacharacters  potential injection risk    I would also recommend always double-quoting variable substitutions in shell conditionals   if   -n   var     then   since something like a -o or other content in the variable could amend your test arguments

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var     a b c     trimmed   echo  var

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This is what I did and worked out perfect and so simple  the string  quot         test quot  the string  echo  the string  echo  quot  the string quot   Output  test

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This worked for me   text     trim my edges       trimmed  text trimmed   trimmed         Remove longest matching series of spaces from the front trimmed   trimmed         Remove longest matching series of spaces from the back  echo   lt  trimmed gt    Adding angle braces just to make it easier to confirm that all spaces are removed   Result  lt trim my edges gt    To put that on fewer lines for the same result   text      trim my edges      trimmed     text

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This is what I did and worked out perfect and so simple  the string  quot         test quot  the string  echo  the string  echo  quot  the string quot   Output  test

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I ve always done it with sed    var  hg st -R   path    sed -e  s            If there is a more elegant solution  I hope somebody posts it

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Trim whitespace from both ends of specified parameter  trim          read -rd     1  lt  lt  lt     1        Unit test for trim    test trim          local foo   1      trim foo     test   foo      2     test trim hey hey  amp  amp  test trim    hey  hey  amp  amp  test trim  ho    ho  amp  amp  test trim  hey ho   hey ho   amp  amp  test trim    hey  ho     hey  ho   amp  amp  test trim    n n t hey n t ho  t n    hey n t ho   amp  amp  test trim    n      amp  amp  test trim   n    n   amp  amp  echo passed

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In order to remove all the spaces from the beginning and the end of a string  including end of line characters    echo  variable   xargs echo -n   This will remove duplicate spaces also   echo    this string has a lot       of spaces     xargs echo -n   Produces   this string has a lot of spaces

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Use AWK   echo  var   awk   gsub               1

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A simple answer is   echo     lol      xargs   Xargs will do the trimming for you  It s one command program  no parameters  returns the trimmed string  easy as that   Note  this doesn t remove all internal spaces so  foo bar  stays the same  it does NOT become  foobar   However  multiple spaces will be condensed to single spaces  so  foo    bar  will become  foo bar   In addition it doesn t remove end of lines characters

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You can use old-school tr  For example  this returns the number of modified files in a git repository  whitespaces stripped   MYVAR  git ls-files -m wc -l tr -d

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While it s not strictly Bash this will do what you want and more   php -r   x   trim    hi there      echo  x     If you want to make it lowercase too  do   php -r   x   trim    Hi There       x   strtolower  x    echo  x

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I had to test the result  numeric  from a command but it seemed the variable with the result was containing spaces and some non printable characters  Therefore even after a  trim  the comparison was erroneous  I solved it by extracting the numerical part from the variable   numerical var   echo   var with result from command    grep -o   0-9

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I ve always done it with sed    var  hg st -R   path    sed -e  s            If there is a more elegant solution  I hope somebody posts it

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I ve always done it with sed    var  hg st -R   path    sed -e  s            If there is a more elegant solution  I hope somebody posts it

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This will remove all the whitespaces from your String     VAR2    VAR2     space           replaces the first occurrence and    all occurrences of whitespaces in the string  I e  all white spaces get replaced by     nothing

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There are a lot of answers  but I still believe my just-written script is worth being mentioned because    it was successfully tested in the shells bash dash busybox shell it is extremely small it doesn t depend on external commands and doesn t need to fork  - fast and low resource usage  it works as expected    it strips all spaces and tabs from beginning and end  but not more important  it doesn t remove anything from the middle of the string  many other answers do   even newlines will remain special  the      joins multiple arguments using one space  if you want to trim  amp  output only the first argument  use   1  instead if doesn t have any problems with matching file name patterns etc    The script   trim       local s2 s        until s2    s    space           s2      s     do s   s2   done   until s2    s    space           s2      s     do s   s2   done   echo   s      Usage   mystring     here     is     something      mystring   trim   mystring   echo   gt  mystring lt     Output    gt here     is     something lt

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This worked for me   text     trim my edges       trimmed  text trimmed   trimmed         Remove longest matching series of spaces from the front trimmed   trimmed         Remove longest matching series of spaces from the back  echo   lt  trimmed gt    Adding angle braces just to make it easier to confirm that all spaces are removed   Result  lt trim my edges gt    To put that on fewer lines for the same result   text      trim my edges      trimmed     text

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Python has a function strip   that works identically to PHP s trim    so we can just do a little inline Python to make an easily understandable utility for this   alias trim  python -c  import sys  sys stdout write sys stdin read   strip        This will trim leading and trailing whitespace  including newlines      x  echo -e   n t    n    trim    if   -z   x     then echo hi  fi hi

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There is a solution which only uses Bash built-ins called wildcards   var      abc        remove leading whitespace characters var    var    var      space           remove trailing whitespace characters var    var    var       space           printf   s       var       Here s the same wrapped in a function   trim         local var            remove leading whitespace characters     var    var    var      space               remove trailing whitespace characters     var    var    var       space               printf   s    var      You pass the string to be trimmed in quoted form  e g     trim     abc       A nice thing about this solution is that it will work with any POSIX-compliant shell   Reference   Remove leading  amp  trailing whitespace from a Bash variable  original source

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To remove spaces and tabs from left to first word  enter   echo       This is a test    sed  s     t        cyberciti biz tips delete-leading-spaces-from-front-of-each-word html

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This trims multiple spaces of the front and end  whatever   whatever       whatever   whatever

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Yet another solution with unit tests which trims  IFS from stdin  and works with any input separator  even    0     ltrim           Left-trim  IFS from stdin as a single line        1  Line separator  default NUL      local trimmed     while IFS  read -r -d    1-   -u 9     do         if   -n    trimmed defined             then             printf  s   REPLY          else             printf  s    REPLY    REPLY     IFS               fi         printf    1- x00           trimmed true     done 9 lt  amp 0      if     REPLY        then           No delimiter at last line         if   -n    trimmed defined             then             printf  s   REPLY          else             printf  s    REPLY    REPLY     IFS               fi     fi    rtrim           Right-trim  IFS from stdin as a single line        1  Line separator  default NUL      local previous last     while IFS  read -r -d    1-   -u 9     do         if   -n    previous defined             then             printf  s   previous              printf    1- x00           fi         previous   REPLY      done 9 lt  amp 0      if     REPLY        then           No delimiter at last line         last   REPLY          printf  s   previous          if   -n    previous defined             then             printf    1- x00           fi     else         last   previous      fi      right whitespace    last      IFS        printf  s    last  right whitespace      trim           Trim  IFS from individual lines        1  Line separator  default NUL      ltrim   1         rtrim   1

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Assignments ignore leading and trailing whitespace and as such can be used to trim     var  echo     hello    echo  var hello

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Removing spaces to one space    text    fmt -su

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trim   removes whitespaces  and tabs  non-printable characters  I am considering just whitespaces for simplicity   My version of a solution   var    hg st -R   path      I often like to enclose shell output in double quotes var    echo    var     sed  s                g      This is my suggestion if   -n   var     then  echo     var    fi   The  sed  command trims only leading and trailing whitespaces  but it can be piped to the first command as well resulting in   var    hg st -R   path    sed  s                g    if   -n   var     then  echo     var    fi

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var    a b    echo    set -f  echo  var     gt a b

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With Bash s extended pattern matching features enabled  shopt -s extglob   you can use this    trimmed         to remove an arbitrary amount of leading spaces

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This does not have the problem with unwanted globbing  also  interior white-space is unmodified  assuming that  IFS is set to the default  which is    t n     It reads up to the first newline  and doesn t include it  or the end of string  whichever comes first  and strips away any mix of leading and trailing space and  t characters  If you want to preserve multiple lines  and also strip leading and trailing newlines   use read -r -d    var  lt  lt  eof instead  note  however  that if your input happens to contain  neof  it will be cut off just before   Other forms of white space  namely  r   f  and  v  are not stripped  even if you add them to  IFS    read -r var  lt  lt  eof  var eof

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I would simply use sed   function trim       echo   1    sed -n  1h 1 H    g s     t    g s    t     g p        a  Example of usage on single-line string  string      wordA wordB  wordC   wordD      trimmed    trim   string     echo  GIVEN STRING    string   echo  TRIMMED STRING    trimmed     Output   GIVEN STRING       wordA wordB  wordC   wordD      TRIMMED STRING   wordA wordB  wordC   wordD    b  Example of usage on multi-line string  string      wordA     gt wordB lt  wordC      trimmed    trim   string     echo -e  GIVEN STRING    string  n  echo  TRIMMED STRING    trimmed     Output   GIVEN STRING       wordAA     gt wordB lt  wordC       TRIMMED STRING   wordAA     gt wordB lt  wordC    c  Final note  If you don t like to use a function  for single-line string you can simply use a  easier to remember  command like   echo   string    sed -e  s     t        sed -e  s    t         Example   echo     wordA wordB wordC       sed -e  s     t        sed -e  s    t         Output   wordA wordB wordC   Using the above on multi-line strings will work as well  but please note that it will cut any trailing leading internal multiple space as well  as GuruM noticed in the comments  string      wordAA      gt four spaces before lt    gt one space before lt       echo   string    sed -e  s     t        sed -e  s    t         Output   wordAA  gt four spaces before lt   gt one space before lt    So if you do mind to keep those spaces  please use the function at the beginning of my answer   d  EXPLANATION of the sed syntax  find and replace  on multi-line strings used inside the function trim   sed -n     If the first line  copy the pattern to the hold buffer 1h   If not the first line  then append the pattern to the hold buffer 1 H   If the last line then               Copy from the hold to the pattern buffer     g       Do the search and replace     s     t    g     s    t     g       print     p

[string] How to trim whitespace from a Bash variable?

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