How to call a function in shell Scripting

Question

I have a shell script which conditionally calls a function   For Example -  if     choice     true    then    process install elif     choice     false    then    process exit fi  process install       commands      commands       process exit       commands      commands        Please let me know how to accomplish this

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Summary    Define functions before using them  Once defined  treat them as commands    Consider this script  called funcdemo      bin bash         0    amp  amp  exhort  write nastygram   exhort        echo  Please  please do not forget to                0    amp  amp  exhort  write begging letter    In use     funcdemo   funcdemo  line 3  exhort  command not found   funcdemo 1 Please  please do not forget to write begging letter     Note the potential for a missing function to lie undiscovered for a long time  think  by a customer at the most critical wrong moment     It only matters whether the function exists when it is executed  the same as it only matters whether any other command exists when you try to execute it   Indeed  until it goes to execute the command  the shell neither knows nor cares whether it is an external command or a function

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The functions need to be defined before being used   There is no mechanism is sh to pre-declare functions  but a common technique is to do something like    main       case   choice  in     true   process install       false  process exit     esac    process install       commands      commands       process exit       commands      commands       main

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You can create another script file separately for the functions and invoke the script file whenever you want to call the function  This will help you to keep your code clean   Function Definition   Create a new script file Function Call         Invoke the script file

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You don t specify which shell  there are many   so I am assuming Bourne Shell  that is I think your script starts with      bin sh   Please remember to tag future questions with the shell type  as this will help the community answer your question   You need to define your functions before you call them  Using      process install         echo  Performing process install   commands  using arguments               process exit         echo  Performing process exit   commands  using arguments                Then you can call your functions  just as if you were calling any command   if     choice     true    then     process install foo bar elif     choice     false    then     process exit baz qux   You may also wish to check for invalid choices at this juncture     else     echo  Invalid choice    choice       fi   See it run with three different values of   choice    Good luck

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bin bash  process install         commands         commands        process exit         commands         commands         if     choice     true    then     process install else     process exit fi

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bin bash     functiontest sh a sample to call the function in the shell script    choice  true    function process install         commands         function process exit       commands           function main         if      choice      true      then         process install   elif      choice      false      then         process exit     fi        main          it will start from the main function

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Example of using a function   in bash      bin bash   file sh  a sample shell script to demonstrate the concept of Bash shell functions   define usage function usage        echo  Usage   0 filename      exit 1      define is file exists function    f - gt  store argument passed to the script is file exists        local f   1         -f   f      amp  amp  return 0    return 1     invoke  usage   call usage   function if filename not supplied       -eq 0     amp  amp  usage    Invoke is file exits if   is file exists   1    then  echo  File found   1  else  echo  File not found   1  fi

[shell] How to call a function in shell Scripting?

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