How to obtain the absolute path of a file via Shell (BASH/ZSH/SH)?

Question

Question: is there a simple sh/bash/zsh/fish/... command to print the absolute path of whichever file I feed it?

Usage case: I'm in directory /a/b and I'd like to print the full path to file c on the command-line so that I can easily paste it into another program: /a/b/c. Simple, yet a little program to do this could probably save me 5 or so seconds when it comes to handling long paths, which in the end adds up. So it surprises me that I can't find a standard utility to do this — is there really none?

Here's a sample implementation, abspath.py:

#!/usr/bin/python
# Author: Diggory Hardy 
# Licence: public domain
# Purpose: print the absolute path of all input paths

import sys
import os.path
if len(sys.argv)>1:
    for i in range(1,len(sys.argv)):
        print os.path.abspath( sys.argv[i] )
    sys.exit(0)
else:
    print >> sys.stderr, "Usage: ",sys.argv[0]," PATH."
    sys.exit(1)

user_737641 · Answer

The simplest if you want to use only builtins is probably:

find `pwd` -name fileName

Only an extra two words to type, and this will work on all unix systems, as well as OSX.

user_1555615 · Answer

The top answers in this question may be misleading in some cases. Imagine that the file, whose absolute path you want to find, is in the $PATH variable:

# node is in $PATH variable
type -P node
# /home/user/.asdf/shims/node
cd /tmp
touch node  # But because there is a file with the same name inside the current dir check out what happens below
readlink -e node
# /tmp/node
readlink -m node
# /tmp/node
readlink -f node
# /tmp/node
echo "$(cd "$(dirname "node")"; pwd -P)/$(basename "node")"
# /tmp/node
realpath node
# /tmp/node
realpath -e node
# /tmp/node

# Now let's say that for some reason node does not exist in current directory
rm node
readlink -e node
# 
readlink -m node    
# /tmp/node         # Note: /tmp/node does not exist, but is printed
readlink -f node
# /tmp/node         # Note: /tmp/node does not exist, but is printed
echo "$(cd "$(dirname "node")"; pwd -P)/$(basename "node")"
# /tmp/node         # Note: /tmp/node does not exist, but is printed
realpath node
# /tmp/node         # Note: /tmp/node does not exist, but is printed
realpath -e node
# realpath: node: No such file or directory

Based on the above I can conclude that: realpath -e and readlink -e can be used for finding the absolute path of a file, that we expect to exist in current directory, without result being affected by the $PATH variable. The only difference is that realpath outputs to stderr, but both will return error code if file is not found:

cd /tmp
rm node
realpath -e node ; echo $?
# realpath: node: No such file or directory
# 1
readlink -e node ; echo $?
# 1

Now in case you want the absolute path a of a file that exists in $PATH, the following command would be suitable, independently on whether a file with same name exists in current dir.

type -P example.txt
# /path/to/example.txt

# Or if you want to follow links
readlink -e $(type -P example.txt)
# /originalpath/to/example.txt

# If the file you are looking for is an executable (and wrap again through `readlink -e` for following links )
which executablefile
# /opt/bin/executablefile

And a, fallback to $PATH if missing, example:

cd /tmp
touch node
echo $(readlink -e node || type -P node)
# /tmp/node
rm node
echo $(readlink -e node || type -P node)
# /home/user/.asdf/shims/node

user_577878 · Answer

Answer with Homebrew

realpath is the best answer, but if you don't have it installed, you must first run brew install coreutils which will install coreutils with lots of awesome functions. Writing a custom function and exporting it is too much work and risk for error for something like this, here are two lines:

$ brew install coreutils
$ realpath your-file-name.json

user_15809 · Answer

The answer of Alexander Klimetschek is okay if your script may insist on a bash or bash compatible shell being present. It won't work with a shell that is only POSIX conforming.

Also when the final file is a file in root, the output will be //file, which is not technically incorrect (double / are treated like single ones by the system) but it looks strange.

Here's a version that works with every POSIX conforming shell, all external tools it is using are also required by the POSIX standard, and it explicitly handles the root-file case:

#!/bin/sh

abspath ( ) {
    if [ ! -e "$1" ]; then
        return 1
    fi

    file=""
    dir="$1"
    if [ ! -d "$dir" ]; then
        file=$(basename "$dir")
        dir=$(dirname "$dir")
    fi

    case "$dir" in
        /*) ;;
        *) dir="$(pwd)/$dir"
    esac
    result=$(cd "$dir" && pwd)

    if [ -n "$file" ]; then
        case "$result" in
            */) ;;
             *) result="$result/"
        esac
        result="$result$file"
    fi

    printf "%s
" "$result"
}

abspath "$1"

Put that into a file and make it executable and you have a CLI tool to quickly get the absolute path of files and directories. Or just copy the function and use it in your own POSIX conforming scripts. It turns relative paths into absolute ones and returns absolute ones as is.

Interesting modifications:

If you replace the line result=$(cd "$dir" && pwd) with result=$(cd "$dir" && pwd -P), then all symbolic links in the path to the final file are resolved as well.

If you are not interested into the first modification, you can optimize the absolute case by returning early:

abspath ( ) {
    if [ ! -e "$1" ]; then
        return 1
    fi

    case "$1" in
        /*)
            printf "%s
" "$1"
            return 0
    esac

    file=""
    dir="$1"
    if [ ! -d "$dir" ]; then
        file=$(basename "$dir")
        dir=$(dirname "$dir")
    fi

    result=$(cd "$dir" && pwd)

    if [ -n "$file" ]; then
        case "$result" in
            */) ;;
            *) result="$result/"
        esac
        result="$result$file"
    fi

    printf "%s
" "$result"
}

And since the question will arise: Why printf instead of echo?

echo is intended primary to print messages for the user to stdout. A lot of echo behavior that script writers rely on is in fact unspecified. Not even the famous -n is standardized or the usage of for tab. The POSIX standard says:

A string to be written to standard output. If the first operand is -n, or if any of the operands contain a character, the results are implementation-defined.
- https://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html

Thus whenever you want to write something to stdout and it's not for the purpose of printing a message to the user, the recommendation is to use printf as the behavior of printf is exactly defined. My function uses stdout to pass out a result, this is not a message for the user and thus only using printf guarantees perfect portability.

user_12101504 · Answer

I use the single line

(cd ${FILENAME%/*}; pwd)

However, this can only be used when $FILENAME has a leading path of any kind (relative or absolute) that actually exists. If there is no leading path at all, then the answer is simply $PWD. If the leading path does not exist, then the answer may be indeterminate, otherwise and the answer is simply ${FILENAME%/*} if the path is absolute.

Putting this all together I would suggest using the following function

function abspath() {
  # argument 1: file pathname (relative or absolute)
  # returns: file pathname (absolute)
  if [ "$1" == "${1##*/}" ]; then # no path at all
    echo "$PWD"
  elif [ "${1:0:1}" == "/" -a "${1/../}" == "$1" ]; then # strictly absolute path
    echo "${1%/*}"
  else # relative path (may fail if a needed folder is non-existent)
    echo "$(cd ${1%/*}; pwd)"
  fi
}

Note also that this only work in bash and compatible shells. I don't believe the substitutions work in the simple shell sh.

How to obtain the absolute path of a file via Shell (BASH/ZSH/SH)?

22 Answers

Answer with Homebrew