Check if file exists and whether it contains a specific string

Question

I want to check if file2 sh exists and also if a specific word  poet is part of the file  I use grep to create the variable used var      bin ksh  file name  home file2 sh                   used var  grep  poet   file name        How can I check if used var has some value

User · Answer

You should use the grep -q flag for quiet output  See the man pages below   man grep output     General Output Control    -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     This KornShell  ksh  script demos the grep quiet output and is a solution to your question   grepUtil ksh       bin ksh   Initialize Variables file poet txt var    dir tempDir dirPath      dir     searchString  poet    Function to initialize variables initialize        echo  Entering initialize      echo  Exiting initialize      Function to create File with Input  Params  1 Directory 2 File 3 String to write to FileName createFileWithInput        echo  Entering createFileWithInput      orgDirectory   PWD      cd   1       gt    2      print   3   gt  gt    2      cd   orgDirectory      echo  Exiting createFileWithInput      Function to create File with Input  Params  1 directoryName createDir        echo  Entering createDir      mkdir -p   1      echo  Exiting createDir      Params  1 FileName readLine        echo  Entering readLine      file   1      while read line     do          assign last line to var         var   line      done  lt   file      echo  Exiting readLine     Check if file exists   Params  1 File doesFileExit        echo  Entering doesFileExit      orgDirectory   PWD      cd   PWD   dirPath       echo   PWD      if    -e    1       then         echo    1  exists      else         echo    1  does not exist      fi     cd   orgDirectory      echo  Exiting doesFileExit     Check if file contains a string quietly  Params  1 Directory Path 2 File 3 String to seach for in File doesFileContainStringQuiet        echo  Entering doesFileContainStringQuiet      orgDirectory   PWD      cd   PWD   1       echo   PWD      grep -q   3    2      if        -eq 0   then         echo    3  found in   2       else         echo    3  not found in   2       fi     cd   orgDirectory      echo  Exiting doesFileContainStringQuiet     Check if file contains a string with output  Params  1 Directory Path 2 File 3 String to seach for in File doesFileContainString        echo  Entering doesFileContainString      orgDirectory   PWD      cd   PWD   1       echo   PWD      grep   3    2      if        -eq 0   then         echo    3  found in   2       else         echo    3  not found in   2       fi     cd   orgDirectory      echo  Exiting doesFileContainString      -----------  ---Main----  ----------- echo  Starting    PWD    0  with Input Parameters   1    1   2    2   3    3    initialize  function call  createDir   dir   function call  createFileWithInput   dir    file    searchString   function call  doesFileExit   file   function call  if        -eq 0   then     doesFileContainStringQuiet   dirPath    file    searchString   function call      doesFileContainString   dirPath    file    searchString   function call  fi echo  Exiting    PWD    0     grepUtil ksh Output    user foo  tmp   ksh grepUtil ksh Starting   tmp grepUtil ksh with Input Parameters   1    2    3  Entering createDir Exiting createDir Entering createFileWithInput Exiting createFileWithInput Entering doesFileExit poet txt exists Exiting doesFileExit Entering doesFileContainStringQuiet poet found in poet txt Exiting doesFileContainStringQuiet Entering doesFileContainString poet poet found in poet txt Exiting doesFileContainString Exiting   tmp grepUtil ksh

User · Answer

test -e will test whether a file exists or not  The test command returns a zero value if the test succeeds or 1 otherwise   Test can be written either as test -e or using       -e   file name     amp  amp  grep  poet   file name   Unless you actually need the output of grep you can test the return value as grep will return 1 if there are no matches and zero if there are any    In general terms you can test if a string is non-empty using    string    which will return 0 if non-empty and 1 if empty

User · Answer

If you have the test binary installed or ksh has a matching built-in function  you could use it to perform your checks  Usually  bin   is a symbolic link to test   if   -e   file name     then   echo  File exists  fi  if   -z   used var     then   echo  Variable is empty  fi

User · Answer

Instead of storing the output of grep in a variable and then checking whether the variable is empty  you can do this   if grep -q  poet   file name then     echo  poet was found in  file name  fi                 Here are some commonly used tests      -d FILE           FILE exists and is a directory    -e FILE           FILE exists    -f FILE           FILE exists and is a regular file    -h FILE           FILE exists and is a symbolic link  same as -L     -r FILE           FILE exists and is readable    -s FILE           FILE exists and has a size greater than zero    -w FILE           FILE exists and is writable    -x FILE           FILE exists and is executable    -z STRING           the length of STRING is zero   Example   if   -e   file name     amp  amp      -z   used var    then     echo   file name exists and  used var is not empty  fi

User · Answer

if test -e   file name  then      fi  if grep -q  poet   file name  then      fi

[shell] Check if file exists and whether it contains a specific string

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