How to Get Bash Script’s Own Path

Bash script may need to get its own path. In normal Bash script, $0 is the path to the script. However, when a script is sourced, such as . a.sh, a.sh‘s $0 does not give a.sh while the caller’s name. How to reliably get a bash script’s own path no matter whether the Bash script is executed or sourced is introduced in this post.

Short answer

You can use ${BASH_SOURCE[0]} to get the script’s own path, in sourced or directly executed Bash script.

Bash and Shell

Why ${BASH_SOURCE[0]} contains the own path

From bash manual:

BASH_SOURCE
An array variable whose members are the source filenames where the corresponding shell function names in the FUNCNAME array variable are defined. The shell function ${FUNCNAME[$i]} is defined in the file ${BASH_SOURCE[$i]} and called from ${BASH_SOURCE[$i+1]}.

What about ${BASH_SOURCE[0]? This following example shows it well.

We have 2 Bash scripts: a.sh and b.sh which is sourced by a.sh and contains a function.

a.sh

#!/bin/bash

echo "\$0: $0"

echo ${FUNCNAME[0]} in ${BASH_SOURCE[0]}

. ./b.sh

b.sh

#!/bin/bash

echo "\$0: $0"

echo ${FUNCNAME[0]} in ${BASH_SOURCE[0]}

fun() {
    echo ${FUNCNAME[0]} in ${BASH_SOURCE[0]}
    echo $0
}

fun

What happens if we run a.sh directly by sh a.sh?

The result is as follows.

$0: a.sh
main in a.sh
$0: a.sh
source in ./b.sh
fun in ./b.sh
a.sh

What about we source a.sh by . a.sh instead of executing it? It gives

$0: bash
source in a.sh
$0: bash
source in ./b.sh
fun in ./b.sh
bash

In summary, in sourced or directly executed bash script files, ${BASH_SOURCE[0] contains the path of the bash source file and ${FUNCNAME[0] contains “source” or “main”. So, ${BASH_SOURCE[0]} gives you a reliable variable for the Bash script source file path no matter whether it is used inside of a function and no matter whether the script is directed executed or sourced.

Eric Zhiqiang Ma

Eric is interested in building high-performance and scalable distributed systems and related technologies. The views or opinions expressed here are solely Eric's own and do not necessarily represent those of any third parties.

2 comments:

  1. //A c function to get your own executable’s execution directory.
    // Sometimes you want to know the program source

    #include
    #include
    #include
    #include
    #include

    #ifndef MAX_PATH
    #define MAX_PATH 256
    #endif

    static char * get_path_to_me(void);
    static char *
    get_path_to_me ()
    {
    static char buffer[MAX_PATH];
    char *cp;
    int len;
    if ((len = readlink (“/proc/self/exe”, buffer, sizeof (buffer) – 1)) != -1)
    {
    buffer[len] = ‘\0′;
    cp=strrchr(buffer,’/’);
    *cp=’\0′;
    fprintf (stderr, “\n%s version 0.9, date Compiled: %s, “, cp+1, __DATE__);
    fprintf (stderr, “is executed from %s\n”, buffer); //program executes, dirname ok
    *cp=’/’;
    }
    else
    *buffer = ‘\0’;
    return (buffer);
    }
    #if 0 // set to 1 to test as stand-alone, leave as 0 if you want to include this function in your code.
    /**
    * @brief main
    * @param argc
    * @param argv
    * @return
    */
    int
    main (int argc, char *argv[])
    {
    char *pgm;
    char *pgmx;
    pgm = strdup (get_path_to_me ());
    strcpy(buffer,pgm);
    printf(“\nfull path = %s, directory=%s program=%s\n”,buffer,dirname(pgm),basename(pgm));
    return 0;
    }
    #endif

    1. Thanks for sharing the C code.

      This is a nice trick:

      readlink (“/proc/self/exe”, buffer, sizeof (buffer) – 1)

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