How can I match a string with a regex in Bash

Question

I am trying to write a bash script that contains a function so when given a  tar   tar bz2   tar gz etc  file it uses tar with the relevant switches to decompress the file   I am using if elif then statements which test the filename to see what it ends with and I cannot get it to match using regex metacharacters   To save constantly rewriting the script I am using  test  at the command line  I thought the statement below should work  I have tried every combination of brackets  quotes and metacharaters possible and still it fails   test sed-4 2 2 tar bz2   tar  bz2   echo     this returns 1  false    I m sure the problem is a simple one and I ve looked everywhere  yet I cannot fathom how to do it   Does someone know how I can do this

User · Answer

I don t have enough rep to comment here  so I m submitting a new answer to improve on dogbane s answer  The dot   in the regexp      sed-4 2 2 tar bz2    tar bz2      amp  amp  echo matched   will actually match any character  not only the literal dot between  tar bz2   for example     sed-4 2 2 tar4bz2    tar bz2      amp  amp  echo matched    sed-4 2 2 tar  bz2    tar bz2      amp  amp  echo matched   or anything that doesn t require escaping with      The strict syntax should then be     sed-4 2 2 tar bz2    tar  bz2      amp  amp  echo matched   or you can go even stricter and also include the previous dot in the regex      sed-4 2 2 tar bz2      tar  bz2      amp  amp  echo matched

User · Answer

shopt -s nocasematch  if    sed-4 2 2  LINE     yes y       then exit 0  fi

User · Answer

Since you are using bash  you don t need to create a child process for doing this  Here is one solution which performs it entirely within bash       TEST                       amp  amp  TEST   BASH REMATCH 1     BASH REMATCH 2     Explanation  The groups before and after the sequence  colon and one or more spaces  are stored by the pattern match operator in the BASH REMATCH array

User · Answer

A Function To Do This  extract        if   -f  1     then       case  1 in             tar bz2    tar xvjf  1                   tar gz     tar xvzf  1                   bz2        bunzip2  1                    rar        rar x  1                      gz         gunzip  1                     tar        tar xvf  1                    tbz2       tar xvjf  1                   tgz        tar xvzf  1                   zip        unzip  1                      Z          uncompress  1                 7z         7z x  1                                  echo  don t know   1               esac   else       echo    1  is not a valid file     fi     Other Note  In response to Aquarius Power in the comment above  We need to store the regex on a var  The variable BASH REMATCH is set after you match the expression  and   BASH REMATCH n   will match the nth group wrapped in parentheses ie in the following   BASH REMATCH 1      compressed  and   BASH REMATCH 2       gz   if     compressed gz              a-z  1 5         then    echo   BASH REMATCH 2      else    echo  Not proper format    fi    The regex above isn t meant to be a valid one for file naming and extensions  but it works for the example

User · Answer

To match regexes you need to use the    operator   Try this      sed-4 2 2 tar bz2    tar bz2      amp  amp  echo matched   Alternatively  you can use wildcards  instead of regexes  with the    operator      sed-4 2 2 tar bz2     tar bz2     amp  amp  echo matched   If portability is not a concern  I recommend using    instead of   or test as it is safer and more powerful  See What is the difference between test    and      for details

User · Answer

if     STR     pattern     then     echo  It is the string   else     echo  It s not him   fi   Works for me  GNU bash  version 4 3 11 1 -release  x86 64-pc-linux-gnu

[regex] How can I match a string with a regex in Bash?

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