In bash how to store a return value in a variable

Question

I know some very basic commands in Linux and am trying to write some scripts  I have written a function which evaluates the sum of last 2-digits in a 5-digit number  The function should concatenate this resultant sum in between the last 2-digits and return it  The reason I want to return this value is because I will be using this value in the other function    Ex  if I have 12345  then my function will calculate 4 5 and return 495      bin bash  set -x echo  enter            read input  function password formula           length    input          last two   input length-2 length          first  echo  last two  sed -e  s        1  g  awk   print  2            second  echo  last two  sed -e  s        1  g  awk   print  1            let sum  first  second         sum len    sum          echo  second         echo  sum          if    sum -gt 9           then                sum   sum 1          fi          value  second sum first         return  value   result   password formula  echo  result   I am trying to echo and see the result but I am getting the output as shown below    -bash-3 2    file2 sh      password formula     echo  enter        read input 12385     length 8     last two 85      echo 85      sed -e  s        1  g       awk   print  2       first 5      echo 85      sed -e  s        1  g       awk   print  1       second 8     let sum 5 8     sum len 2     echo 5     echo 8     echo 13         13 -gt 9         sum 3     value 835     return 835    result  enter   5 8 13     echo enter  5 8 13 enter  5 8 13   I also tried to print the result as   password formula RESULT    echo  RESULT   But that is giving some unknown value       RESULT 67    echo 67 67   How can I properly store the correct value and print  to double check  on the screen    Thanks in advance

User · Answer

Simplest answer    the return code from a function can be only a value in the range from 0 to 255   To store this value in a variable you have to do like in this example      bin bash  function returnfunction         example value between 0-255 to be returned      return 23      note that the value has to be stored immediately after the function call   returnfunction myreturnvalue     echo  myreturnvalue is   myreturnvalue

User · Answer

Something like this could be used  and still maintaining meanings of return  to return control signals  and echo  to return information  and logging statements  to print debug info messages    v verbose 1 v verbose f              verbose file name FLAG BGPID     e verbose             if     v verbose -ge 0     then                 v verbose f   tempfile                  tail -f  v verbose f  amp                  FLAG BGPID              fi    d verbose             if    x  FLAG BGPID      x      then                 kill  FLAG BGPID  gt   dev null                 FLAG BGPID                    rm -f  v verbose f  gt   dev null         fi    init             e verbose          trap cleanup SIGINT SIGQUIT SIGKILL SIGSTOP SIGTERM SIGHUP SIGTSTP    cleanup             d verbose    init  fun1         echo  got  1   gt  gt   v verbose f     echo  got  2   gt  gt   v verbose f     echo       1    2         return 0    a   fun1 10 20  if       -eq 0     then     echo   gt  gt sum   a  else     echo  error      fi cleanup   In here  I m redirecting debug messages to separate file  that is watched by tail  and if there is any changes then printing the change  trap is used to make sure that background process always ends   This behavior can also be achieved using redirection to  dev stderr  But difference can be seen at the time of piping output of one command to input of other command

User · Answer

The return value  aka exit code  is a value in the range 0 to 255 inclusive  It s used to indicate success or failure  not to return information  Any value outside this range will be wrapped   To return information  like your number  use  echo   value    To print additional information that you don t want captured  use  echo  my irrelevant info   gt  amp 2    Finally  to capture it  use what you did    result   password formula    In other words   echo  enter            read input  password formula             length    input          last two   input length-2 length          first  echo  last two  sed -e  s        1  g  awk   print  2            second  echo  last two  sed -e  s        1  g  awk   print  1            let sum  first  second         sum len    sum          echo  second  gt  amp 2         echo  sum  gt  amp 2          if    sum -gt 9           then                sum   sum 1          fi          value  second sum first         echo  value   result   password formula  echo  The value is  result

User · Answer

It is easy you need to echo the value you need to return and then capture it like below  demofunc        local variable  hellow      echo  variable        val   demofunc  echo  val

User · Answer

The answer above suggests changing the function to echo data rather than return it so that it can be captured   For a function or program that you can t modify where the return value needs to be saved to a variable  like test    which returns a 0 1 success value   echo    within the command substitution     Test if we re remote  isRemote    test -z   REMOTE ADDR   echo        Or  isRemote      -z   REMOTE ADDR     echo         Additionally you may want to reverse the 0  success    1  error  values   for your own sanity  using arithmetic expansion  remoteAddrIsEmpty      -z   REMOTE ADDR     echo    1-         E g     echo  REMOTE ADDR    test -z   REMOTE ADDR   echo    0   REMOTE ADDR 127 0 0 1   test -z   REMOTE ADDR   echo    1   retval    test -z   REMOTE ADDR   echo       echo  retval 1   unset REMOTE ADDR   retval    test -z   REMOTE ADDR   echo       echo  retval 0   For a program which prints data but also has a return value to be saved  the return value would be captured separately from the output     Two different files  1 and 2    cat 1 1   cat 2 2   diffs    cmp 1 2     haveDiffs      echo  Have differences    haveDiffs  Diffs    diffs   Have differences   1  Diffs   1 2 differ  char 1  line 1    diffs    cmp 1 1     haveDiffs      echo  Have differences    haveDiffs  Diffs    diffs   Have differences   0  Diffs        Or again  if you just want a success variable  reverse with arithmetic expansion    cmp -s 1 2  filesAreIdentical    1-       echo  filesAreIdentical 0

User · Answer

It s due to the echo statements  You could switch your echos to prints and return with an echo  Below works     bin bash  set -x echo  enter    read input  function password formula           length    input          last two   input length-2 length          first  echo  last two  sed -e  s        1  g  awk   print  2            second  echo  last two  sed -e  s        1  g  awk   print  1            let sum  first  second         sum len    sum          print  second         print  sum          if    sum -gt 9           then            sum   sum 1          fi          value  second sum first         echo  value   result   password formula  echo  result

User · Answer

Use the special bash variable  quot    quot  like so  function output   my function  function return value

[linux] In bash, how to store a return value in a variable?

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