How can I check if a program exists from a Bash script

Question

How would I validate that a program exists  in a way that will either return an error and exit  or continue with the script   It seems like it should be easy  but it s been stumping me

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If you guys gals can t get the things in answers here to work and are pulling hair out of your back  try to run the same command using bash -c  Just look at this somnambular delirium  This is what really happening when you run   sub-command    First  It can give you completely different output     command -v ls alias ls  ls --color auto    bash -c  command -v ls   bin ls   Second  It can give you no output at all     command -v nvm nvm   bash -c  command -v nvm    bash -c  nvm --help  bash  nvm  command not found

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This will tell according to the location if the program exist or not       if   -x  usr bin yum    then         echo  This is Centos      fi

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I couldn t get one of the solutions to work  but after editing it a little I came up with this  Which works for me   dpkg --get-selections   grep -q linux-headers-  uname -r   if      -eq 1    then         apt-get install linux-headers-  uname -r  fi

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I d say there isn t any portable and 100  reliable way due to dangling aliases  For example   alias john  ls --color  alias paul  george -F  alias george  ls -h  alias ringo     Of course  only the last one is problematic  no offence to Ringo    But all of them are valid aliases from the point of view of command -v   In order to reject dangling ones like ringo  we have to parse the output of the shell built-in alias command and recurse into them  command -v isn t a superior to alias here   There isn t any portable solution for it  and even a Bash-specific solution is rather tedious   Note that a solution like this will unconditionally reject alias ls  ls -F    test     command -v  1   grep -qv alias

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I never did get the previous answers to work on the box I have access to  For one  type has been installed  doing what more does   So the builtin directive is needed  This command works for me   if    builtin type -p vim     then echo  TRUE   else echo  FALSE   fi

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Script     bin bash    Commands found in the hash table are checked for existence before being   executed and non-existence forces a normal PATH search  shopt -s checkhash  function exists      local mycomm  1  shift    return 1   hash  mycomm 2 gt  dev null       printf   xe2 x9c x98  ABRT    mycomm  command does not exist n   return 1    readonly -f exists  exists notacmd exists bash hash bash -c  printf  Fin  n     Result     ABRT   notacmd  command does not exist hits    command    0     usr bin bash Fin

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There are a ton of options here  but I was surprised no quick one-liners  This is what I used at the beginning of my scripts         command -v mvn           echo  mvn is not installed  1 gt  amp 2   exit 1          command -v java           echo  java is not installed  1 gt  amp 2   exit 1      This is based on the selected answer here and another source

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Check for multiple dependencies and inform status to end users  for cmd in latex pandoc  do   printf   -10s    cmd    if hash   cmd  2 gt  dev null  then     echo OK   else     echo missing   fi done   Sample output   latex     OK pandoc    missing   Adjust the 10 to the maximum command length  It is not automatic  because I don t see a non-verbose POSIX way to do it  How can I align the columns of a space separated table in Bash   Check if some apt packages are installed with dpkg -s and install them otherwise   See  Check if an apt-get package is installed and then install it if it  39 s not on Linux  It was previously mentioned at  How can I check if a program exists from a Bash script

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I use this  because it s very easy   if    LANG C type example 2 gt  dev null wc -l    1   then echo exists else echo  not exists  fi   or  if    LANG C type example 2 gt  dev null wc -l    1   then echo exists else echo  not exists  fi   It uses shell builtins and programs  echo status to standard output and nothing to standard error  On the other hand  if a command is not found  it echos status only to standard error

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If there isn t any external type command available  as taken for granted here   we can use POSIX compliant env -i sh -c  type cmd 1  dev null 2  amp 1      Portable version of Bash s type -P cmd  without output on stdout  typep        command -p env -i PATH   PATH  sh -c         export LC ALL C LANG C       cmd   1        cmd   type   cmd  2 gt  dev null      echo  error  command  cmd not found  exiting      1 gt  amp 2  exit 1                    0    amp  amp  exit 1       case   cmd  in                exit 0                  printf   s n   error   cmd  1 gt  amp 2  exit 1         esac          1     exit 1      Get your standard  PATH value  PATH    command -p getconf PATH   typep ls typep builtin typep ls-temp   At least on Mac OS X v10 6 8  Snow nbsp Leopard  using Bash 4 2 24 2  command -v ls does not match a moved  bin ls-temp

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Try using   test -x filename   or    -x filename     From the Bash manpage under Conditional Expressions     -x file           True if file exists and is executable

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checkexists         while   -n   1     do           -n    which   1         echo   1   command not found         shift     done

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GIT  usr bin git                       STORE THE RELATIVE PATH   GIT   which git                      USE THIS COMMAND TO SEARCH FOR THE RELATIVE PATH  if      -e  GIT     then               CHECK IF THE FILE EXISTS     echo  PROGRAM DOES NOT EXIST       exit 1                             EXIT THE PROGRAM IF IT DOES NOT fi    DO SOMETHING      exit 0                                 EXIT THE PROGRAM IF IT DOES

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My setup for a Debian server   I had the problem when multiple packages contained the same name   For example apache2  So this was my solution   function  apt install         apt-get install -y  1  gt   dev null    function  apt install norecommends         apt-get install -y --no-install-recommends  1  gt   dev null   function  apt available         if    apt-cache search  1   grep -o   1    uniq   wc -l     1     then         echo  Package is available    1          PACKAGE INSTALL  1      else         echo  Package  1 is NOT available for install          echo   We can not continue without this package             echo   Exitting now            exit 0     fi   function  package install        apt available  1     if      PACKAGE INSTALL      1     then         if      dpkg-query -l  1   tail -n1   cut -c1-2      ii     then              echo   package is already installed   1          else             echo   installing package    1  please wait                 apt install  1             sleep 0 5         fi     fi    function  package install no recommends        apt available  1     if      PACKAGE INSTALL      1     then         if      dpkg-query -l  1   tail -n1   cut -c1-2      ii     then              echo   package is already installed   1          else             echo   installing package    1  please wait                 apt install norecommends  1             sleep 0 5         fi     fi

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I agree with lhunath to discourage use of which  and his solution is perfectly valid for Bash users  However  to be more portable  command -v shall be used instead     command -v foo  gt  dev null 2 gt  amp 1      echo  I require foo but it s not installed   Aborting    gt  amp 2  exit 1      Command command is POSIX compliant  See here for its specification  command - execute a simple command  Note  type is POSIX compliant  but type -P is not

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Assuming you are already following safe shell practices   set -eu -o pipefail shopt -s failglob    dummy --version 2 gt  amp 1  gt  dev null   This assumes the command can be invoked in such a way that it does  almost  nothing  like reporting its version or showing help   If the dummy command is not found  Bash exits with the following error       my-script  line 8  dummy  command not found   This is more useful and less verbose than the other command -v  and similar  answers because the error message is auto generated and also contains a relevant line number

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In case you want to check if a program exists and is really a program  not a Bash built-in command  then command  type and hash are not appropriate for testing as they all return 0 exit status for built-in commands   For example  there is the time program which offers more features than the time built-in command  To check if the program exists  I would suggest using which as in the following example     First check if the time program exists timeProg  which time  if     timeProg         then   echo  The time program does not exist on this system     exit 1 fi    Invoke the time program  timeProg --quiet -o result txt -f   S  U   p  du -sk   echo  Total CPU time   dc -f result txt  seconds  rm result txt

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To mimic Bash s type -P cmd  we can use the POSIX compliant env -i type cmd 1  dev null 2  amp 1   man env    The option  -i  causes env to completely ignore the environment it inherits     In other words  there are no aliases or functions to be looked up by the type command   ls     echo  Hello  world       ls type ls env -i type ls  cmd ls cmd lsx env -i type  cmd 1 gt  dev null 2 gt  amp 1      echo   cmd not found   exit 1

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The which command might be useful  man which  It returns 0 if the executable is found and returns 1 if it s not found or not executable   NAME         which - locate a command  SYNOPSIS         which  -a  filename      DESCRIPTION         which returns the pathnames of the files which would        be executed in the current environment  had its        arguments been given as commands in a strictly        POSIX-conformant shell  It does this by searching        the PATH for executable files matching the names        of the arguments   OPTIONS         -a     print all matching pathnames of each argument  EXIT STATUS         0      if all specified commands are                found and executable         1      if one or more specified commands is nonexistent               or not executable         2      if an invalid option is specified   The nice thing about which is that it figures out if the executable is available in the environment that which is run in - it saves a few problems

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Late answer but this is what I ended up doing  I just check if the command I execute returns an error code  If it returns 0 it means program is installed  Moreover you can use this to check the output of a script  Take for instance this script  foo sh    bin bash echo  quot hello world quot  exit 1   throw some error code  Examples    outputs something bad    and exits bash foo sh    -eq 0    echo  quot something bad happened  not installed quot    exit 1    does NOT outputs nothing nor exits because dotnet is installed on my machine dotnet --version    -eq 0    echo  quot something bad happened  not installed quot    exit 1  Basically all this is doing is checking the exit code of a command run  the most accepted answer on this question will return true even if the command exit code is not 0

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Use Bash builtins if you can   which programname        type -P programname

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Expanding on  lhunath s and  GregV s answers  here s the code for the people who want to easily put that check inside an if statement   exists       command -v   1   gt  dev null 2 gt  amp 1     Here s how to use it   if exists bash  then   echo  Bash exists   else   echo  Your system does not have Bash  fi

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Answer POSIX compatible  command -v  lt the command gt   Example use  if   command -v COMMAND  amp  gt   dev null then     echo  quot COMMAND could not be found quot      exit fi  For Bash specific environments  hash  lt the command gt    For regular commands  Or    type  lt the command gt    To check built-ins and keywords  Explanation Avoid which  Not only is it an external process you re launching for doing very little  meaning builtins like hash  type or command are way cheaper   you can also rely on the builtins to actually do what you want  while the effects of external commands can easily vary from system to system  Why care   Many operating systems have a which that doesn t even set an exit status  meaning the if which foo won t even work there and will always report that foo exists  even if it doesn t  note that some POSIX shells appear to do this for hash too   Many operating systems make which do custom and evil stuff like change the output or even hook into the package manager   So  don t use which  Instead use one of these    command -v foo  gt  dev null 2 gt  amp 1      echo  gt  amp 2  quot I require foo but it s not installed   Aborting  quot   exit 1      type foo  gt  dev null 2 gt  amp 1      echo  gt  amp 2  quot I require foo but it s not installed   Aborting  quot   exit 1      hash foo 2 gt  dev null      echo  gt  amp 2  quot I require foo but it s not installed   Aborting  quot   exit 1      Minor side-note  some will suggest 2 gt  amp - is the same 2 gt  dev null but shorter     this is untrue   2 gt  amp - closes FD 2 which causes an error in the program when it tries to write to stderr  which is very different from successfully writing to it and discarding the output  and dangerous    If your hash bang is  bin sh then you should care about what POSIX says  type and hash s exit codes aren t terribly well defined by POSIX  and hash is seen to exit successfully when the command doesn t exist  haven t seen this with type yet    command s exit status is well defined by POSIX  so that one is probably the safest to use  If your script uses bash though  POSIX rules don t really matter anymore and both type and hash become perfectly safe to use  type now has a -P to search just the PATH and hash has the side-effect that the command s location will be hashed  for faster lookup next time you use it   which is usually a good thing since you probably check for its existence in order to actually use it  As a simple example  here s a function that runs gdate if it exists  otherwise date  gnudate         if hash gdate 2 gt  dev null  then         gdate  quot    quot      else         date  quot    quot      fi    Alternative with a complete feature set You can use scripts-common to reach your need  To check if something is installed  you can do  checkBin  lt the command gt     errorMessage  quot This tool requires  lt the command gt   Install it please  and then run this tool again  quot

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hash foo 2 gt  dev null  works with Z shell  Zsh   Bash  Dash and ash   type -p foo  it appears to work with Z shell  Bash and ash  BusyBox   but not Dash  it interprets -p as an argument    command -v foo  works with Z shell  Bash  Dash  but not ash  BusyBox   -ash  command  not found    Also note that builtin is not available with ash and Dash

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The hash-variant has one pitfall  On the command line you can for example type in  one folder process   to have process executed  For this the parent folder of one folder must be in  PATH  But when you try to hash this command  it will always succeed   hash one folder process  echo      will always output  0

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The following is a portable way to check whether a command exists in  PATH and is executable     -x    command -v foo       Example   if     -x    command -v git      then   echo  Error  git is not installed    gt  amp 2   exit 1 fi   The executable check is needed because bash returns a non-executable file if no executable file with that name is found in  PATH   Also note that if a non-executable file with the same name as the executable exists earlier in  PATH  dash returns the former  even though the latter would be executed  This is a bug and is in violation of the POSIX standard   Bug report   Standard   In addition  this will fail if the command you are looking for has been defined as an alias

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If you check for program existence  you are probably going to run it later anyway  Why not try to run it in the first place   if foo --version  gt  dev null 2 gt  amp 1  then     echo Found else     echo Not found fi   It s a more trustworthy check that the program runs than merely looking at PATH directories and file permissions   Plus you can get some useful result from your program  such as its version   Of course the drawbacks are that some programs can be heavy to start and some don t have a --version option to immediately  and successfully  exit

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Use   if     command --help      then   echo  This command exists  else   echo  This command does not exist   fi   Put in a working switch  such as  --help  or  -v  in the if check  if    command --help     then

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I second the use of  command -v   E g  like this   md   command -v mkdirhier    alias md   md  mkdir     bash  emacs    command -v emacs  -nw     emacs nano alias e  emacs    -z   command -v jed      amp  amp  alias jed  emacs

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It could be simpler  just      usr bin env bash                                                                 set -x                                                                                 if local program  foo  returns 1  doesn t exist  then                                                                                   if   type -P foo  then                                                                  echo  crap  no foo                                                              else                                                                                    echo  sweet  we have foo                                                       fi                                                                                    Change foo to vi to get the other condition to fire

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I have a function defined in my  bashrc that makes this easier   command exists          type   1   amp  gt   dev null       Here s an example of how it s used  from my  bash profile    if command exists mvim   then     export VISUAL  mvim --nofork  fi

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It depends on whether you want to know whether it exists in one of the directories in the  PATH variable or whether you know the absolute location of it  If you want to know if it is in the  PATH variable  use  if which programname  gt  dev null  then     echo exists else     echo does not exist fi   otherwise use  if   -x  path to programname    then     echo exists else     echo does not exist fi   The redirection to  dev null  in the first example suppresses the output of the which program

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For those interested  none of the methodologies in previous answers work if you wish to detect an installed library  I imagine you are left either with physically checking the path  potentially for header files and such   or something like this  if you are on a Debian-based distribution    dpkg --status libdb-dev   grep -q not-installed  if      -eq 0    then     apt-get install libdb-dev fi   As you can see from the above  a  0  answer from the query means the package is not installed  This is a function of  grep  - a  0  means a match was found  a  1  means no match was found

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To use hash  as  lhunath suggests  in a Bash script   hash foo  amp  gt   dev null if      -eq 1    then     echo  gt  amp 2  foo not found   fi   This script runs hash and then checks if the exit code of the most recent command  the value stored in     is equal to 1  If hash doesn t find foo  the exit code will be 1  If foo is present  the exit code will be 0    amp  gt   dev null redirects standard error and standard output from hash so that it doesn t appear onscreen and echo  gt  amp 2 writes the message to standard error

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I would just try and call the program with for example --version or --help and check if the command succeeded or failed  Used with set -e  the script will exit if the program is not found  and you will get a meaningful error message      bin bash set -e git --version  gt  gt   dev null

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Command -v works fine if the POSIX BUILTINS option is set for the  lt command gt  to test for  but it can fail if not   It has worked for me for years  but I recently ran into one where it didn t work   I find the following to be more failproof  test -x  quot   which  lt command gt   quot   Since it tests for three things  path  existence and execution permission

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I had to check if Git was installed as part of deploying our CI server  My final Bash script was as follows  Ubuntu server    if   builtin type -p git  amp  gt  dev null  then   sudo apt-get -y install git-core fi

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I wanted the same question answered but to run within a Makefile   install       if      -x    shell command -v ghead       then           echo  ghead does not exist  Please install it              exit -1        fi

[bash] How can I check if a program exists from a Bash script?

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