How to split one string into multiple strings separated by at least one space in bash shell

Question

I have a string containing many words with at least one space between each two  How can I split the string into individual words so I can loop through them   The string is passed as an argument  E g    2      cat cat  file   How can I loop through it   Also  how can I check if a string contains spaces

User · Accepted Answer

Did you try just passing the string variable to a for loop? Bash, for one, will split on whitespace automatically.

sentence="This is   a sentence."
for word in $sentence
do
    echo $word
done

This
is
a
sentence.

User · Answer

Probably the easiest and most secure way in BASH 3 and above is  var  quot string    to  split quot  read -ra arr  lt  lt  lt  quot  var quot    where arr is the array which takes the split parts of the string  or  if there might be newlines in the input and you want more than just the first line  var  quot string    to  split quot  read -ra arr -d     lt  lt  lt  quot  var quot    please note the space in -d     it cannot be omitted   but this might give you an unexpected newline from  lt  lt  lt  quot  var quot   as this implicitly adds an LF at the end   Example  touch NOPE var  quot   a    quot  read -ra arr  lt  lt  lt  quot  var quot  for a in  quot   arr     quot   do echo  quot   a  quot   done  Outputs the expected      a       as this solution  in contrast to all previous solutions here  is not prone to unexpected and often uncontrollable shell globbing  Also this gives you the full power of IFS as you probably want  Example  IFS   read -ra arr  lt   lt  grep  quot   USER  quot   etc passwd  for a in  quot   arr     quot   do echo  quot   a  quot   done  Outputs something like   tino   x   1000   1000   Valentin Hilbig    home tino    bin bash   As you can see  spaces can be preserved this way  too  IFS   read -ra arr  lt  lt  lt   split      this      for a in  quot   arr     quot   do echo  quot   a  quot   done  outputs   split        this       Please note that the handling of IFS in BASH is a subject on its own  so do your tests  some interesting topics on this   unset IFS  Ignores runs of SPC  TAB  NL and on line starts and ends IFS     No field separation  just reads everything IFS      Runs of SPC  and SPC only   Some last examples  var    n nthis is n n na test n n  IFS    n  read -ra arr -d     lt  lt  lt  quot  var quot  i 0  for a in  quot   arr     quot   do let i    echo  quot  i   a  quot   done  outputs 1  this is  2  a test   while unset IFS var    n nthis is n n na test n n  read -ra arr -d     lt  lt  lt  quot  var quot  i 0  for a in  quot   arr     quot   do let i    echo  quot  i   a  quot   done  outputs 1  this  2  is  3  a  4  test   BTW   If you are not used to   ANSI-ESCAPED-STRING  get used to it  it s a timesaver   If you do not include -r  like in read -a arr  lt  lt  lt  quot  var quot   then read does backslash escapes   This is left as exercise for the reader     For the second question  To test for something in a string I usually stick to case  as this can check for multiple cases at once  note  case only executes the first match  if you need fallthrough use multiple case statements   and this need is quite often the case  pun intended   case  quot  var quot  in                    empty var                    variable is empty                    have space  quot  var quot             have SPC     space          have whitespace  quot  var quot        have whitespaces like TAB    -   A-Za-z0-9    have nonalnum  quot  var quot         non-alphanum-chars found   -                have punctuation  quot  var quot       some punctuation chars found                    default case  quot  var quot           if all above does not match esac  So you can set the return value to check for SPC like this  case  quot  var quot  in         true       false   esac  Why case   Because it usually is a bit more readable than regex sequences  and thanks to Shell metacharacters it handles 99  of all needs very well

User · Answer

Just use the shells  quot set quot  built-in  For example  set  text  After that  individual words in  text will be in  1   2   3  etc  For robustness  one usually does set -- junk  text shift  to handle the case where  text is empty or start with a dash  For example  text  quot This is          a              test quot  set -- junk  text shift for word  do   echo  quot   word  quot  done  This prints  This   is   a   test

User · Answer

A  To split a sentence into its words  space separated  you can simply use the default IFS by using  array    string      Example running the following snippet     bin bash  sentence  this is the   sentence      you  want to split  words    sentence    len     words      echo  words counted   len   printf   s n     words         print array   will output  words counted  8 this is the  sentence   you  want to split   As you can see you can use single or double quotes too without any problem  Notes  -- this is basically the same of mob s answer  but in this way you store the array for any further needing  If you only need a single loop  you can use his answer  which is one line shorter    -- please refer to this question for alternate methods to split a string based on delimiter    B  To check for a character in a string you can also use a regular expression match  Example to check for the presence of a space character you can use   regex   s 1    if      sentence      regex        then         echo  Space here    fi

User · Answer

echo  This is   a sentence     tr -s       012  This is a sentence    For checking for spaces  use grep     echo  This is   a sentence     grep      gt   dev null   echo    0   echo  Thisisasentence     grep      gt   dev null        echo    1

User · Answer

I like the conversion to an array  to be able to access individual elements   sentence  this is a story  stringarray   sentence    now you can access individual elements directly  it starts with 0    echo   stringarray 0     or convert back to string in order to loop   for i in    stringarray      do         do whatever on  i done   Of course looping through the string directly was answered before  but that answer had the the disadvantage to not keep track of the individual elements for later use   for i in  sentence do         do whatever on  i done   See also Bash Array Reference

User · Answer

echo  WORDS   xargs -n1 echo   This outputs every word  you can process that list as you see fit afterwards

User · Answer

For checking spaces just with bash        str       str          amp  amp  echo  no spaces     echo  has spaces

[bash] How to split one string into multiple strings separated by at least one space in bash shell?

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