Reliable way for a Bash script to get the full path to itself

Question

I have a Bash script that needs to know its full path  I m trying to find a broadly-compatible way of doing that without ending up with relative or funky-looking paths  I only need to support Bash  not sh  csh  etc   What I ve found so far    The accepted answer to Getting the source directory of a Bash script from within addresses getting the path of the script via dirname  0  which is fine  but that may return a relative path  like     which is a problem if you want to change directories in the script and have the path still point to the script s directory  Still  dirname will be part of the puzzle  The accepted answer to Bash script absolute path with OS X  OS X specific  but the answer works regardless  gives a function that will test to see if  0 looks relative and if so will pre-pend  PWD to it  But the result can still have relative bits in it  although overall it s absolute  nbsp  mdash  for instance  if the script is t in the directory  usr bin and you re in  usr and you type bin    bin t to run it  yes  that s convoluted   you end up with  usr bin    bin as the script s directory path  Which works  but    The readlink solution on this page  which looks like this     Absolute path to this script   home user bin foo sh SCRIPT   readlink -f  0    Absolute path this script is in   home user bin SCRIPTPATH  dirname  SCRIPT    But readlink isn t POSIX and apparently the solution relies on GNU s readlink where BSD s won t work for some reason  I don t have access to a BSD-like system to check     So  various ways of doing it  but they all have their caveats   What would be a better way  Where  better  means    Gives me the absolute path  Takes out funky bits even when invoked in a convoluted way  see comment on  2 above    E g   at least moderately canonicalizes the path   Relies only on Bash-isms or things that are almost certain to be on most popular flavors of  nix systems  GNU Linux  BSD and BSD-like systems like OS nbsp X  etc    Avoids calling external programs if possible  e g   prefers Bash built-ins    Updated  thanks for the heads up  wich  It doesn t have to resolve symlinks  in fact  I d kind of prefer it left them alone  but that s not a requirement

User · Answer

As realpath is not installed per default on my Linux system, the following works for me:

SCRIPT="$(readlink --canonicalize-existing "$0")"
SCRIPTPATH="$(dirname "$SCRIPT")"

$SCRIPT will contain the real file path to the script and $SCRIPTPATH the real path of the directory containing the script.

Before using this read the comments of this answer.

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Just for the hell of it I ve done a bit of hacking on a script that does things purely textually  purely in Bash  I hope I caught all the edge cases   Note that the   var  pat repl  that I mentioned in the other answer doesn t work since you can t make it replace only the shortest possible match  which is a problem for replacing  foo     as e g         will take everything before it  not just a single entry  And since these patterns aren t really regexes I don t see how that can be made to work  So here s the nicely convoluted solution I came up with  enjoy      By the way  let me know if you find any unhandled edge cases      bin bash  canonicalize path       local path   1    OIFS   IFS    IFS        read -a parts  lt   lt  echo   path     IFS   OIFS     local i    parts       local j 0   local back 0   local -a rev canon   while    i  gt  0    do       i--       case    parts  i    in                            back                if    back  gt  0    then              back--            else            rev canon j     parts  i                 j              fi       esac   done   while    j  gt  0    do       j--       echo -n     rev canon  j      done   echo    canonicalize path                 foo   bar  foo bar      bar    foo bar             foo   bar

User · Answer

The simplest way that I have found to get a full canonical path in Bash is to use cd and pwd    ABSOLUTE PATH    cd    dirname    BASH SOURCE 0       amp  amp  pwd    basename    BASH SOURCE 0        Using   BASH SOURCE 0   instead of  0 produces the same behavior regardless of whether the script is invoked as  lt name gt  or source  lt name gt

User · Answer

Try this   cd   dirname     -L  0    amp  amp  readlink -f  0    echo  0

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Perhaps the accepted answer to the following question may be of help  How can I get the behavior of GNU  39 s readlink -f on a Mac  Given that you just want to canonicalize the name you get from concatenating  PWD and  0  assuming that  0 is not absolute to begin with   just use a series of regex replacements along the line of abs dir   abs dir            and such  Yes  I know it looks horrible  but it ll work and is pure Bash

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Easy to read  Below is an alternative  It ignores symlinks     bin bash currentDir      cd   dirname   0     pwd    echo -n  current   pwd echo script  currentDir     Since I posted the above answer a couple years ago  I ve evolved my practice to using this linux specific paradigm  which properly handles symlinks   ORIGIN   dirname   readlink -f  0

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If we use Bash I believe this is the most convenient way as it doesn t require calls to any external commands   THIS PATH    BASH SOURCE 0     THIS DIR   dirname  THIS PATH

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I m surprised that the realpath command hasn t been mentioned here  My understanding is that it is widely portable   ported   Your initial solution becomes   SCRIPT  realpath  0  SCRIPTPATH  dirname  SCRIPT    And to leave symbolic links unresolved per your preference   SCRIPT  realpath -s  0  SCRIPTPATH  dirname  SCRIPT

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Get the absolute path of a shell script  It does not use the -f option in readlink  and it should therefore work on BSD Mac nbsp OS nbsp X   Supports   source   script  When called by the   dot operator  Absolute path  path to script Relative path like   script  path dir1    dir2 dir3    script When called from symlink When symlink is nested eg  foo- gt dir1 dir2 bar bar- gt      doe doe- gt script When caller changes the scripts name   I am looking for corner cases where this code does not work  Please let me know   Code  pushd    gt   dev null SCRIPT PATH    BASH SOURCE 0     while   -h    SCRIPT PATH       do     cd   dirname    SCRIPT PATH         SCRIPT PATH    readlink   basename    SCRIPT PATH        done cd   dirname    SCRIPT PATH      gt   dev null SCRIPT PATH   pwd    popd   gt   dev null echo  srcipt    SCRIPT PATH    echo  pwd      pwd      Known issus  The script must be on disk somewhere  Let it be over a network  If you try to run this script from a PIPE it will not work  wget -o  dev null -O - http   host domain dir script sh  bash   Technically speaking  it is undefined  Practically speaking  there is no sane way to detect this   A co-process can not access the environment of the parent

User · Answer

One liner   dirname   realpath  0

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More simply  this is what works for me   MY DIR  dirname  0  source  MY DIR  inc db sh

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You may try to define the following variable   CWD    cd -P --    dirname --    BASH SOURCE 0       amp  amp  pwd -P     Or you can try the following function in Bash   realpath            1          amp  amp  echo   1     echo   PWD   1          This function takes one argument  If the argument already has an absolute path  print it as it is  otherwise print  PWD variable   filename argument  without    prefix    Related    Bash script absolute path with OS X Get the source directory of a Bash script from within the script itself

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Considering this issue again   there is a very popular solution that is referenced within this thread that has its origin here   DIR     cd     dirname    BASH SOURCE 0        amp  amp  pwd      I have stayed away from this solution because of the use of dirname - it can present cross-platform difficulties  particularly if a script needs to be locked down for security reasons   But as a pure Bash alternative  how about using   DIR     cd     echo    BASH SOURCE 0           amp  amp  pwd      Would this be an option

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Use   SCRIPT PATH   dirname  which  0     which prints to standard output the full path of the executable that would have been executed when the passed argument had been entered at the shell prompt  which is what  0 contains   dirname strips the non-directory suffix from a file name   Hence you end up with the full path of the script  no matter if the path was specified or not

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Bourne shell  sh  compliant way   SCRIPT HOME  dirname  0   while read a  do cd  a  amp  amp  pwd  amp  amp  break  done

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We have placed our own product realpath-lib on GitHub for free and unencumbered community use   Shameless plug but with this Bash library you can     get realpath  lt absolute relative symlink local file gt    This function is the core of the library   function get realpath      if    -f   1     then        file  must  exist     if cd    echo    1         amp  gt  dev null     then            file  may  not be local           exception is   file ext           try  cd    cd -    works           local tmppwd   PWD          cd -  amp  gt  dev null     else            file  must  be local         local tmppwd   PWD      fi else        file  cannot  exist     return 1   failure fi    reassemble realpath echo   tmppwd     1       return 0   success      It doesn t require any external dependencies  just Bash 4    Also contains functions to get dirname  get filename  get stemname and validate path validate realpath   It s free  clean  simple and well documented  so it can be used for learning purposes too  and no doubt can be improved   Try it across platforms   Update   After some review and testing we have replaced the above function with something that achieves the same result  without using dirname  only pure Bash  but with better efficiency   function get realpath               -f   1      amp  amp  return 1   failure   file does not exist         -n   no symlinks      amp  amp  local pwdp  pwd -P     local pwdp  pwd    do symlinks      echo     cd     echo    1         2 gt  dev null   pwdp       1         echo result      return 0   success      This also includes an environment setting no symlinks that provides the ability to resolve symlinks to the physical system   By default it keeps symlinks intact

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Yet another way to do this      shopt -s extglob  selfpath  0 selfdir   selfpath            while    -L   selfpath     do   selfpath   readlink   selfpath     if        selfpath           then     selfpath   selfdir   selfpath    fi   selfdir   selfpath           done  echo  selfpath  selfdir

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Simply   BASEDIR   readlink -f  0   xargs dirname    Fancy operators are not needed

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I have used the following approach successfully for a while  not on OS nbsp X though   and it only uses a shell built-in and handles the  source foobar sh  case as far as I have seen   One issue with the  hastily put together  example code below is that the function uses  PWD which may or may not be correct at the time of the function call  So that needs to be handled      bin bash  function canonical path         Handle relative vs absolute path       1 0 1            amp  amp  x  1    x  PWD  1     Change to dirname of x   cd   x         Combine new pwd with basename of x   echo   pwd -P    x        cd  OLDPWD    echo   canonical path    BASH SOURCE 0      type   type cd type echo type pwd

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Here s what I ve come up with  edit  plus some tweaks provided by sfstewman  levigroker  Kyle Strand  and Rob Kennedy   that seems to mostly fit my  better  criteria   SCRIPTPATH     cd    dirname   0     gt  dev null 2 gt  amp 1   pwd -P      That SCRIPTPATH line seems particularly roundabout  but we need it rather than SCRIPTPATH  pwd  in order to properly handle spaces and symlinks   The inclusion of output redirection   gt  dev null 2 gt  amp 1  handles the rare    case where cd might produce output that would interfere with the surrounding          capture   Such as cd being overridden to also ls a directory after switching to it    Note also that esoteric situations  such as executing a script that isn t coming from a file in an accessible file system at all  which is perfectly possible   is not catered to there  or in any of the other answers I ve seen

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I just had to revisit this issue today and found Get the source directory of a Bash script from within the script itself   DIR     cd     dirname    BASH SOURCE 0        amp  amp  pwd      There s more variants at the linked answer  e g  for the case where the script itself is a symlink

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The accepted solution has the inconvenient  for me  to not be  source-able   if you call it from a  source       yourScript    0 would be  bash    The following function  for bash    3 0  gives me the right path  however the script might be called  directly or through source  with an absolute or a relative path    by  right path   I mean the full absolute path of the script being called  even when called from another path  directly or with  source       bin bash echo  0 executed  function bashscriptpath       local  sp  1   local ascript   0    local asp    dirname  0      echo  b1 asp   asp   b1 ascript   ascript     if      asp          amp  amp    ascript      bash   amp  amp    ascript         bashrc       then asp    BASH SOURCE 0         elif      asp          amp  amp    ascript         bashrc       then asp   pwd    else     if      ascript      bash       then       ascript   BASH SOURCE 0         asp    dirname  ascript       fi        echo  b2 asp   asp   b2 ascript   ascript       if       ascript          ascript      then asp  asp       elif       ascript            ascript      then       asp   pwd        while       ascript            ascript      do         asp   asp             ascript   ascript            done     elif       ascript           ascript       then       if      asp              then asp   pwd    else asp    pwd    asp    fi     fi     fi     eval   sp    asp      bashscriptpath H export H   H    The key is to detect the  source  case and to use   BASH SOURCE 0   to get back the actual script

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Answering this question very late  but I use   SCRIPT    readlink -m    type -p  0           Full path to script BASE DIR  dirname   SCRIPT                    Directory script is run in NAME  basename   SCRIPT                       Actual name of script even if linked

[bash] Reliable way for a Bash script to get the full path to itself

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