Checking Bash exit status of several commands efficiently

Question

Is there something similar to pipefail for multiple commands  like a  try  statement but within bash  I would like to do something like this   echo  trying stuff  try       command1     command2     command3     And at any point  if any command fails  drop out and echo out the error of that command  I don t want to have to do something like   command1 if      -ne 0    then     echo  command1 borked it  fi  command2 if      -ne 0    then     echo  command2 borked it  fi   And so on    or anything like   pipefail -o command1  arg1   arg2    command2  arg1   arg2    command3   Because the arguments of each command I believe  correct me if I m wrong  will interfere with each other  These two methods seem horribly long-winded and nasty to me so I m here appealing for a more efficient method

User · Answer

For fish shell users who stumble on this thread   Let foo be a function that does not  return   echo  a value  but it sets the exit code as usual  To avoid checking  status after calling the function  you can do   foo  and echo success  or echo failure   And if it s too long to fit on one line   foo  and begin   echo success end  or begin   echo failure end

User · Answer

For what it s worth  a shorter way to write code to check each command for success is   command1    echo  command1 borked it  command2    echo  command2 borked it    It s still tedious but at least it s readable

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An alternative is simply to join the commands together with  amp  amp  so that the first one to fail prevents the remainder from executing   command1  amp  amp    command2  amp  amp    command3   This isn t the syntax you asked for in the question  but it s a common pattern for the use case you describe   In general the commands should be responsible for printing failures so that you don t have to do so manually  maybe with a -q flag to silence errors when you don t want them    If you have the ability to modify these commands  I d edit them to yell on failure  rather than wrap them in something else that does so     Notice also that you don t need to do   command1 if      -ne 0    then   You can simply say   if   command1  then   And when you do need to check return codes use an arithmetic context instead of       -ne   ret      do something if    ret    0     then

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suppose alias command1  grep a  lt  lt  lt abc  alias command2  grep x  lt  lt  lt abc  alias command3  grep c  lt  lt  lt abc   either   command1 1 gt  dev null      echo  quot cmd1 fail quot    bin false       amp  amp  echo  quot cmd1 succeed quot   amp  amp    command2 1 gt  dev null      echo  quot cmd2 fail quot    bin false       amp  amp  echo  quot cmd2 succeed quot   amp  amp    command3 1 gt  dev null      echo  quot cmd3 fail quot    bin false       amp  amp  echo  quot cmd3 succeed quot   or     command1 1 gt  dev null  amp  amp  echo  quot cmd1 succeed quot          echo  quot cmd1 fail quot    bin false       amp  amp      command2 1 gt  dev null  amp  amp  echo  quot cmd2 succeed quot          echo  quot cmd2 fail quot    bin false       amp  amp      command3 1 gt  dev null  amp  amp  echo  quot cmd3 succeed quot          echo  quot cmd3 fail quot    bin false       yields cmd1 succeed cmd2 fail  Tedious it is  But the readability isn t bad

User · Answer

You can write a function that launches and tests the command for you  Assume command1 and command2 are environment variables that have been set to a command   function mytest                local status        if    status    0     then         echo  error with  1   gt  amp 2     fi     return  status    mytest   command1  mytest   command2

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Instead of creating runner functions or using set -e  use a trap   trap  echo  error   do cleanup failed  exit  ERR trap  echo  received signal to stop   do cleanup interrupted  exit  SIGQUIT SIGTERM SIGINT  do cleanup      rm tempfile  echo   1   date    gt  gt  script log     command1 command2 command3   The trap even has access to the line number and the command line of the command that triggered it  The variables are  BASH LINENO and  BASH COMMAND

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What do you mean by  drop out and echo the error    If you mean you want the script to terminate as soon as any command fails  then just do   set -e      DON T do this   See commentary below    at the start of the script  but note warning below    Do not bother echoing the error message  let the failing command handle that   In other words  if you do      bin sh  set -e      Use caution   eg  don t do this command1 command2 command3   and command2 fails  while printing an error message to stderr  then it seems that you have achieved what you want    Unless I misinterpret what you want    As a corollary  any command that you write must behave well  it must report errors to stderr instead of stdout  the sample code in the question prints errors to stdout  and it must exit with a non-zero status when it fails    However  I no longer consider this to be a good practice   set -e has changed its semantics with different versions of bash  and although it works fine for a simple script  there are so many edge cases that it is essentially unusable    Consider things like  set -e  foo     false  echo should not print      foo  amp  amp  echo ok  The semantics here are somewhat reasonable  but if you refactor code into a function that relied on the option setting to terminate early  you can easily get bitten    IMO it is better to write       bin sh   command1    exit  command2    exit  command3    exit   or      bin sh  command1  amp  amp  command2  amp  amp  command3

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Checking status in functional manner  assert exit status        lambda         local val fd   echo      tr -d       cut -d    -f2      local arg  1     shift     shift     local cmd   echo      xargs -E          local val   cat  val fd      eval  arg  val     eval  cmd        local lambda  1   shift    eval      local ret       lambda    lt  echo  ret       Usage   assert exit status  lambda status - gt      status -ne 0     amp  amp  echo Status is  status   lls   Output  Status is 127

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run            if      -ne 0     then     echo  quot    failed with exit code    quot      return 1   else     return 0   fi    run command1  amp  amp  run command2  amp  amp  run command3

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Personally I much prefer to use a lightweight approach  as seen here   yell     echo   0       gt  amp 2    die     yell       exit 111    try             die  cannot        asuser     sudo su -   1  -c      2        Example usage   try apt-fast upgrade -y try asuser vagrant  echo  uname -a   gt  gt     profile

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I ve developed an almost flawless try  amp  catch implementation in bash  that allows you to write code like   try      echo  Hello      false     echo  This will not be displayed   catch      echo  Error in    EXCEPTION SOURCE   at line     EXCEPTION LINE       You can even nest the try-catch blocks inside themselves   try       echo  Hello       try           echo  Nested Hello          false         echo  This will not execute        catch           echo  Nested Caught       EXCEPTION LINE                false     echo  This will not execute too     catch       echo  Error in    EXCEPTION SOURCE   at line     EXCEPTION LINE         The code is a part of my bash boilerplate framework  It further extends the idea of try  amp  catch with things like error handling with backtrace and exceptions  plus some other nice features     Here s the code that s responsible just for try  amp  catch   set -o pipefail shopt -s expand aliases declare -ig   oo  insideTryCatch 0    if try-catch is nested  then set  e before so the parent handler doesn t catch us alias try         oo  insideTryCatch -gt 0     amp  amp  set  e               oo  insideTryCatch  1    set -e             trap   Exception Capture    LINENO      ERR   alias catch      Exception Extract           Exception Capture         local script    BASH SOURCE 1            if      -f  tmp stored exception source     then         echo   script   gt   tmp stored exception source     fi     if      -f  tmp stored exception line     then         echo   1   gt   tmp stored exception line     fi     return 0    Exception Extract         if       oo  insideTryCatch -gt 1        then         set -e     fi        oo  insideTryCatch  -1        EXCEPTION CATCH       Exception GetLastException         local retVal  1     if     retVal -gt 0        then           BACKWARDS COMPATIBILE WAY            export   EXCEPTION SOURCE        EXCEPTION CATCH         EXCEPTION CATCH      -1               export   EXCEPTION LINE        EXCEPTION CATCH         EXCEPTION CATCH      -2             export   EXCEPTION SOURCE        EXCEPTION CATCH   -1            export   EXCEPTION LINE        EXCEPTION CATCH   -2            export   EXCEPTION        EXCEPTION CATCH      0       EXCEPTION CATCH       - 2            return 1   so that we may continue with a  catch      fi    Exception GetLastException         if    -f  tmp stored exception     amp  amp     -f  tmp stored exception line     amp  amp     -f  tmp stored exception source        then         cat  tmp stored exception         cat  tmp stored exception line         cat  tmp stored exception source     else         echo -e    n  BASH LINENO 1   n  BASH SOURCE 2           fi      rm -f  tmp stored exception  tmp stored exception line  tmp stored exception source     return 0     Feel free to use  fork and contribute - it s on GitHub

User · Answer

Sorry that I can not make a comment to the first answer But you should use new instance to execute the command  cmd output           bin bash  function check exit       cmd output           local status        echo  status     if    status -ne 0    then         echo  error with  1   gt  amp 2     fi     return  status    function run command         exit 1    check exit run command

User · Answer

You can use  john-kugelman  s awesome solution found above on non-RedHat systems by commenting out this line in his code      etc init d functions   Then  paste the below code at the end  Full disclosure  This is just a direct copy  amp  paste of the relevant bits of the above mentioned file taken from Centos 7   Tested on MacOS and Ubuntu 18 04    BOOTUP color RES COL 60 MOVE TO COL  echo -en   033   RES COL G  SETCOLOR SUCCESS  echo -en   033 1 32m  SETCOLOR FAILURE  echo -en   033 1 31m  SETCOLOR WARNING  echo -en   033 1 33m  SETCOLOR NORMAL  echo -en   033 0 39m   echo success             BOOTUP     color     amp  amp   MOVE TO COL     echo -n             BOOTUP     color     amp  amp   SETCOLOR SUCCESS     echo -n     OK            BOOTUP     color     amp  amp   SETCOLOR NORMAL     echo -n         echo -ne   r      return 0    echo failure             BOOTUP     color     amp  amp   MOVE TO COL     echo -n             BOOTUP     color     amp  amp   SETCOLOR FAILURE     echo -n   FAILED          BOOTUP     color     amp  amp   SETCOLOR NORMAL     echo -n         echo -ne   r      return 1    echo passed             BOOTUP     color     amp  amp   MOVE TO COL     echo -n             BOOTUP     color     amp  amp   SETCOLOR WARNING     echo -n   PASSED          BOOTUP     color     amp  amp   SETCOLOR NORMAL     echo -n         echo -ne   r      return 1    echo warning             BOOTUP     color     amp  amp   MOVE TO COL     echo -n             BOOTUP     color     amp  amp   SETCOLOR WARNING     echo -n   WARNING          BOOTUP     color     amp  amp   SETCOLOR NORMAL     echo -n         echo -ne   r      return 1

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When I use ssh I need to distinct between problems caused by connection issues and error codes of remote command in errexit  set -e  mode  I use the following function     prepare environment on calling site   rssh  ssh -o ConnectionTimeout 5 -l root  remote ip   function exit255       local flags  -     set  e              local status        set - flags     if     status    255        then         exit 255     else         return  status     fi   export -f exit255    callee   set -e set -o pipefail      rssh        remote ip          type -t exit255       function      rjournaldir   var log journal  if exit255  rssh       -d   rjournaldir       then      rssh  mkdir   rjournaldir    fi rconf   etc systemd journald conf  if        rssh  grep   Storage auto    rconf        then      rssh  sed -i  s  Storage auto Storage persistent     rconf   fi  rssh systemctl reenable systemd-journald service  rssh systemctl is-enabled systemd-journald service  rssh systemctl restart systemd-journald service sleep 1  rssh systemctl status systemd-journald service  rssh systemctl is-active systemd-journald service

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I have a set of scripting functions that I use extensively on my Red Hat system  They use the system functions from  etc init d functions to print green    OK    and red  FAILED  status indicators   You can optionally set the  LOG STEPS variable to a log file name if you want to log which commands fail   Usage  step  Installing XFS filesystem tools   try rpm -i xfsprogs-  rpm next  step  Configuring udev   try cp   rules  etc udev rules d try udevtrigger next  step  Adding rc postsysinit hook   try cp rc postsysinit  etc rc d  try ln -s rc d rc postsysinit  etc rc postsysinit try echo    nexec  etc rc postsysinit   gt  gt   etc rc sysinit next   Output  Installing XFS filesystem tools            OK    Configuring udev                         FAILED  Adding rc postsysinit hook                 OK      Code     bin bash     etc init d functions    Use step    try    and next   to perform a series of commands and print      OK    or  FAILED  at the end  The step as a whole fails if any individual   command fails      Example        step  Remounting   and  boot as read-write         try mount -o remount rw         try mount -o remount rw  boot       next step         echo -n           STEP OK 0        -w  tmp     amp  amp  echo  STEP OK  gt   tmp step       try           Check for  -b  argument to run command in the background      local BG           1    -b     amp  amp    BG 1  shift            1    --     amp  amp          shift           Run the command      if    -z  BG     then                  else               amp      fi        Check if command failed and update  STEP OK if so      local EXIT CODE         if     EXIT CODE -ne 0     then         STEP OK  EXIT CODE            -w  tmp     amp  amp  echo  STEP OK  gt   tmp step             if    -n  LOG STEPS     then             local FILE   readlink -m    BASH SOURCE 1                 local LINE   BASH LINENO 0                echo   FILE  line  LINE  Command       failed with exit code  EXIT CODE    gt  gt    LOG STEPS          fi     fi      return  EXIT CODE    next            -f  tmp step        amp  amp    STEP OK    lt   tmp step      rm -f  tmp step               STEP OK -eq 0      amp  amp  echo success    echo failure     echo      return  STEP OK

[bash] Checking Bash exit status of several commands efficiently

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