How to check if a file contains a specific string using Bash

Question

I want to check if a file contains a specific string or not in bash  I used this script  but it doesn t work    if     grep  SomeString   File     then      Some Actions  fi   What s wrong in my code

User · Answer

In addition to other answers  which told you how to do what you wanted  I try to explain what was wrong  which is what you wanted   In Bash  if is to be followed with a command  If the exit code of this command is equal to 0  then the then part is executed  else the else part if any is executed   You can do that with any command as explained in other answers  if  bin true  then      fi     is an internal bash command dedicated to some tests  like file existence  variable comparisons  Similarly   is an external command  it is located typically in  usr bin    that performs roughly the same tests but needs   as a final argument  which is why   must be padded with a space on the left  which is not the case with      Here you needn t    nor     Another thing is the way you quote things  In bash  there is only one case where pairs of quotes do nest  it is    command  argument     But in  grep  SomeString   File  you have only one word  because  grep   is a quoted unit  which is concatenated with SomeString and then again concatenated with    File   The variable  File is not even replaced with its value because of the use of single quotes  The proper way to do that is grep  SomeString    File

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Try this   if      grep  SomeString   File       then    echo  Found  else    echo  Not Found  fi

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I done this  seems to work fine  if grep  SearchTerm  FileToSearch  then    echo   SearchTerm found OK  else    echo   SearchTerm not found  fi

User · Answer

grep -q  PATTERN   FILE   amp  amp  echo      The exit status is 0  true  if the pattern was found  otherwise blankstring

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if grep -q SomeString   File   then   Some Actions   SomeString was found fi   You don t need       here  Just run the command directly  Add -q option when you don t need the string displayed when it was found   The grep command returns 0 or 1 in the exit code depending on the result of search  0 if something was found  1 otherwise     echo hello   grep hi   echo    1   echo hello   grep he   echo    hello 0   echo hello   grep -q he   echo    0   You can specify commands as an condition of if  If the command returns 0 in its exitcode that means that the condition is true  otherwise false     if  bin true  then echo that is true  fi that is true   if  bin false  then echo that is true  fi     As you can see you run here the programs directly  No additional    or

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if grep -q  string   filename  then      whatever action  fi   Example   if grep -q  my cat is in a tree   tmp cat txt then     mkdir cat fi

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In case if you want to check whether file does not contain a specific string  you can do it as follows   if   grep -q SomeString   File   then   Some Actions   SomeString was not found fi

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Shortest  correct  version   grep -q  something  file       -eq 0    amp  amp  echo  yes     echo  no    can be also written as  grep -q  something  file  test    -eq 0  amp  amp  echo  yes     echo  no    but you dont need to explicitly test it in this case  so the same with   grep -q  something  file  amp  amp  echo  yes     echo  no

User · Answer

To check for a particular  string in a file  cd PATH TO YOUR DIRECTORY  Changing directory to your working directory File YOUR FILENAME   if grep -q STRING YOU ARE CHECKING FOR   File     note the space after the string you are searching for then echo  Hooray  It s available  else echo  Oops  Not available  fi

User · Answer

In case you want to checkif the string matches the whole line and if it  is a fixed string  You can do it this way  grep -Fxq  String   filePath    example   searchString  Hello World   file    test log   if grep -Fxq   searchString   file     then             echo  String found in  file      else             echo  String not found in  file   fi   From the man file   -F  --fixed-strings            Interpret  PATTERN  as  a  list of fixed strings  separated by newlines  any of   which is to be matched             -F is specified by POSIX   -x  --line-regexp           Select only those matches that exactly match the whole line    -x is specified by   POSIX   -q  --quiet  --silent           Quiet  do not write anything to standard output   Exit immediately with zero   status  if  any  match  is           found   even  if  an error was detected   Also see the -s or --no-messages   option    -q is specified by           POSIX

User · Answer

grep -q  something  file       -eq 0     amp  amp  echo  yes     echo  no

[bash] How to check if a file contains a specific string using Bash

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