Case insensitive comparison of strings in shell script

Question

The    operator is used to compare two strings in shell script  However  I want to compare two strings ignoring case  how can it be done  Is there any standard command for this

User · Answer

In Bash  you can use parameter expansion to modify a string to all lower- upper-case   var1 TesT var2 tEst  echo   var1      var2    echo   var1      var2

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if you have bash  str1  MATCH  str2  match  shopt -s nocasematch case   str1  in   str2   echo  match        echo  no match    esac   otherwise  you should tell us what shell you are using   alternative  using awk  str1  MATCH  str2  match  awk -vs1   str1  -vs2   str2   BEGIN     if   tolower s1     tolower s2         print  match

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grep has a -i flag which means case insensitive so ask it to tell you if var2 is in var1   var1 match  var2 MATCH  if echo  var1   grep -i     var2     gt   dev null   then     echo  MATCH  fi

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Save the state of nocasematch  in case some other function is depending on it being disabled    local orig nocasematch   shopt -p nocasematch  shopt -s nocasematch     foo      Foo      amp  amp  echo  match     echo  notmatch   orig nocasematch   Note  only use local if it s inside a function

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All of these answers ignore the easiest and quickest way to do this  as long as you have Bash 4    if      var1          var2        then   echo      fi   All you re doing there is converting both strings to lowercase and comparing the results

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Very easy if you fgrep to do a case-insensitive line compare   str1  MATCH  str2  match   if      fgrep -ix  str1  lt  lt  lt   str2      then     echo  case-insensitive match   fi

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One way would be to convert both strings to upper or lower   test   echo  string     bin tr    upper       lower         echo  String     bin tr    upper       lower      amp  amp  echo same    echo different   Another way would be to use grep   echo  string    grep -qi   String    amp  amp  echo same    echo different

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Here is my solution using tr   var1 match var2 MATCH var1  echo  var1   tr   A-Z     a-z    var2  echo  var2   tr   A-Z     a-z    if     var1      var2      then   echo  MATCH  fi

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For zsh the syntax is slightly different  but still shorter than most answers here    gt  str1  mAtCh   gt  str2  MaTcH   gt       str1 u      str2 u      amp  amp  echo  Strings Match   Strings Match   gt    This will convert both strings to uppercase before the comparison     Another method makes use zsh s globbing flags  which allows us to directly make use of case-insensitive matching by using the i glob flag   setopt extendedglob     str1     i  str2     amp  amp  echo  Match success      str1     i match     amp  amp  echo  Match success

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I came across this great blog tutorial whatever about dealing with case sensitive pattern  The following three methods are explained in details with examples  1  Convert pattern to lowercase using tr command opt    tr    upper       lower     lt  lt  lt  quot  1 quot    case  opt in         sql                  echo  quot Running mysql backup using mysqldump tool    quot                             sync                  echo  quot Running backup using rsync tool    quot                             tar                  echo  quot Running tape backup using tar tool    quot                                                echo  quot Other options quot                     esac  2  Use careful globbing with case patterns opt  1 case  opt in          Ss  Qq  Ll                   echo  quot Running mysql backup using mysqldump tool    quot                              Ss  Yy  Nn  Cc                   echo  quot Running backup using rsync tool    quot                              Tt  Aa  Rr                   echo  quot Running tape backup using tar tool    quot                                                echo  quot Other option quot                     esac  3  Turn on nocasematch opt  1 shopt -s nocasematch case  opt in         sql                  echo  quot Running mysql backup using mysqldump tool    quot                             sync                  echo  quot Running backup using rsync tool    quot                             tar                  echo  quot Running tape backup using tar tool    quot                                                echo  quot Other option quot                     esac  shopt -u nocasematch

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shopt -s nocaseglob

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For korn shell  I use typeset built-in command  -l for lower-case and -u for upper-case    var True typeset -l var if     var     true      then     print  match  fi

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