There's a realpath() C function that'll do the job, but I'm not seeing anything available on the command-line. Here's a quick and dirty replacement:
#!/bin/bash
realpath() {
[[ $1 = /* ]] && echo "$1" || echo "$PWD/${1#./}"
}
realpath "$0"
This prints the path verbatim if it begins with a /. If not it must be a relative path, so it prepends $PWD to the front. The #./ part strips off ./ from the front of $1.
These three simple steps are going to solve this and many other OS X issues:
brew install coreutilsgrealpath .(3) may be changed to just realpath, see (2) output
I found the answer a bit wanting for a few reasons:
in particular, they don't resolve multiple levels of symbolic links, and they are extremely "Bash-y".
While the original question does explicitly ask for a "Bash script", it also makes mention of Mac OS X's BSD-like, non-GNU readlink.
So here's an attempt at some reasonable portability (I've checked it with bash as 'sh' and dash), resolving an arbitrary number of symbolic links; and it should also work with whitespace in the path(s).
This answer was previously edited, re-adding the local bashism. The point of this answer is a portable, POSIX solution. I have edited it to address variable scoping by changing it to a subshell function, rather than an inline one. Please do not edit.
#!/bin/sh
realpath() (
OURPWD=$PWD
cd "$(dirname "$1")"
LINK=$(readlink "$(basename "$1")")
while [ "$LINK" ]; do
cd "$(dirname "$LINK")"
LINK=$(readlink "$(basename "$1")")
done
REALPATH="$PWD/$(basename "$1")"
cd "$OURPWD"
echo "$REALPATH"
)
realpath "$@"
Hope that can be of some use to someone.
I was looking for a solution for use in a system provision script, i.e., run before Homebrew is even installed. Lacking a proper solution I'd just offload the task to a cross-platform language, e.g., Perl:
script_abspath=$(perl -e 'use Cwd "abs_path"; print abs_path(@ARGV[0])' -- "$0")
More often what we actually want is the containing directory:
here=$(perl -e 'use File::Basename; use Cwd "abs_path"; print dirname(abs_path(@ARGV[0]));' -- "$0")
Since there is a realpath as others have pointed out:
// realpath.c
#include <stdio.h>
#include <stdlib.h>
int main (int argc, char* argv[])
{
if (argc > 1) {
for (int argIter = 1; argIter < argc; ++argIter) {
char *resolved_path_buffer = NULL;
char *result = realpath(argv[argIter], resolved_path_buffer);
puts(result);
if (result != NULL) {
free(result);
}
}
}
return 0;
}
Makefile:
#Makefile
OBJ = realpath.o
%.o: %.c
$(CC) -c -o $@ $< $(CFLAGS)
realpath: $(OBJ)
gcc -o $@ $^ $(CFLAGS)
Then compile with make and put in a soft link with:ln -s $(pwd)/realpath /usr/local/bin/realpath
So as you can see above, I took a shot at this about 6 months ago. I totally forgot about it until I found myself in need of a similar thing again. I was completely shocked to see just how rudimentary it was; I've been teaching myself to code pretty intensively for about a year now, but I often feel like maybe I haven't learned anything at all when things are at their worst.
I would remove the 'solution' above, but I really like it sort of being a record of of how much I really have learnt over the past few months.
But I digress. I sat down and worked it all out last night. The explanation in the comments should be sufficient. If you want to track the copy I'm continuing to work on, you can follow this gist. This probably does what you need.
#!/bin/sh # dash bash ksh # !zsh (issues). G. Nixon, 12/2013. Public domain.
## 'linkread' or 'fullpath' or (you choose) is a little tool to recursively
## dereference symbolic links (ala 'readlink') until the originating file
## is found. This is effectively the same function provided in stdlib.h as
## 'realpath' and on the command line in GNU 'readlink -f'.
## Neither of these tools, however, are particularly accessible on the many
## systems that do not have the GNU implementation of readlink, nor ship
## with a system compiler (not to mention the requisite knowledge of C).
## This script is written with portability and (to the extent possible, speed)
## in mind, hence the use of printf for echo and case statements where they
## can be substituded for test, though I've had to scale back a bit on that.
## It is (to the best of my knowledge) written in standard POSIX shell, and
## has been tested with bash-as-bin-sh, dash, and ksh93. zsh seems to have
## issues with it, though I'm not sure why; so probably best to avoid for now.
## Particularly useful (in fact, the reason I wrote this) is the fact that
## it can be used within a shell script to find the path of the script itself.
## (I am sure the shell knows this already; but most likely for the sake of
## security it is not made readily available. The implementation of "$0"
## specificies that the $0 must be the location of **last** symbolic link in
## a chain, or wherever it resides in the path.) This can be used for some
## ...interesting things, like self-duplicating and self-modifiying scripts.
## Currently supported are three errors: whether the file specified exists
## (ala ENOENT), whether its target exists/is accessible; and the special
## case of when a sybolic link references itself "foo -> foo": a common error
## for beginners, since 'ln' does not produce an error if the order of link
## and target are reversed on the command line. (See POSIX signal ELOOP.)
## It would probably be rather simple to write to use this as a basis for
## a pure shell implementation of the 'symlinks' util included with Linux.
## As an aside, the amount of code below **completely** belies the amount
## effort it took to get this right -- but I guess that's coding for you.
##===-------------------------------------------------------------------===##
for argv; do :; done # Last parameter on command line, for options parsing.
## Error messages. Use functions so that we can sub in when the error occurs.
recurses(){ printf "Self-referential:\n\t$argv ->\n\t$argv\n" ;}
dangling(){ printf "Broken symlink:\n\t$argv ->\n\t"$(readlink "$argv")"\n" ;}
errnoent(){ printf "No such file: "$@"\n" ;} # Borrow a horrible signal name.
# Probably best not to install as 'pathfull', if you can avoid it.
pathfull(){ cd "$(dirname "$@")"; link="$(readlink "$(basename "$@")")"
## 'test and 'ls' report different status for bad symlinks, so we use this.
if [ ! -e "$@" ]; then if $(ls -d "$@" 2>/dev/null) 2>/dev/null; then
errnoent 1>&2; exit 1; elif [ ! -e "$@" -a "$link" = "$@" ]; then
recurses 1>&2; exit 1; elif [ ! -e "$@" ] && [ ! -z "$link" ]; then
dangling 1>&2; exit 1; fi
fi
## Not a link, but there might be one in the path, so 'cd' and 'pwd'.
if [ -z "$link" ]; then if [ "$(dirname "$@" | cut -c1)" = '/' ]; then
printf "$@\n"; exit 0; else printf "$(pwd)/$(basename "$@")\n"; fi; exit 0
fi
## Walk the symlinks back to the origin. Calls itself recursivly as needed.
while [ "$link" ]; do
cd "$(dirname "$link")"; newlink="$(readlink "$(basename "$link")")"
case "$newlink" in
"$link") dangling 1>&2 && exit 1 ;;
'') printf "$(pwd)/$(basename "$link")\n"; exit 0 ;;
*) link="$newlink" && pathfull "$link" ;;
esac
done
printf "$(pwd)/$(basename "$newlink")\n"
}
## Demo. Install somewhere deep in the filesystem, then symlink somewhere
## else, symlink again (maybe with a different name) elsewhere, and link
## back into the directory you started in (or something.) The absolute path
## of the script will always be reported in the usage, along with "$0".
if [ -z "$argv" ]; then scriptname="$(pathfull "$0")"
# Yay ANSI l33t codes! Fancy.
printf "\n\033[3mfrom/as: \033[4m$0\033[0m\n\n\033[1mUSAGE:\033[0m "
printf "\033[4m$scriptname\033[24m [ link | file | dir ]\n\n "
printf "Recursive readlink for the authoritative file, symlink after "
printf "symlink.\n\n\n \033[4m$scriptname\033[24m\n\n "
printf " From within an invocation of a script, locate the script's "
printf "own file\n (no matter where it has been linked or "
printf "from where it is being called).\n\n"
else pathfull "$@"
fi
On macOS, the only solution that I've found to this that reliably handles symlinks is by using realpath. Since this requires brew install coreutils, I just automated that step. My implementation looks like this:
#!/usr/bin/env bash
set -e
if ! which realpath >&/dev/null; then
if ! which brew >&/dev/null; then
msg="ERROR: This script requires brew. See https://brew.sh for installation instructions."
echo "$(tput setaf 1)$msg$(tput sgr0)" >&2
exit 1
fi
echo "Installing coreutils/realpath"
brew install coreutils >&/dev/null
fi
thisDir=$( dirname "`realpath "$0"`" )
echo "This script is run from \"$thisDir\""
This errors if they don't have brew installed, but you could alternatively just install that too. I just didn't feel comfortable automating something that curls arbitrary ruby code from the net.
Note that this an automated variation on Oleg Mikheev's answer.
One good test of any of these solutions is:
ln -s) to that fileDoes the solution dereference the symlink, and give you the original directory? If so, it works.
This seems to work for OSX, doesnt require any binaries, and was pulled from here
function normpath() {
# Remove all /./ sequences.
local path=${1//\/.\//\/}
# Remove dir/.. sequences.
while [[ $path =~ ([^/][^/]*/\.\./) ]]; do
path=${path/${BASH_REMATCH[0]}/}
done
echo $path
}
I checked every answered, but missed the best one (IMHO) by Jason S Jul 14 '16 at 3:12, left the comment field.
So here it is, in case someone like me having the tendency to check answered and don't have time to go through every single comments:
$( cd "$(dirname "$0")" ; pwd -P )
Help:
NAME
pwd -- return working directory name
SYNOPSIS
pwd [-L | -P]
DESCRIPTION
The pwd utility writes the absolute pathname of the current working
directory to the standard output.
Some shells may provide a builtin pwd command which is similar or identi-
cal to this utility. Consult the builtin(1) manual page.
The options are as follows:
-L Display the logical current working directory.
-P Display the physical current working directory (all symbolic
links resolved).
I needed a realpath replacement on OS X, one that operates correctly on paths with symlinks and parent references just like readlink -f would. This includes resolving symlinks in the path before resolving parent references; e.g. if you have installed the homebrew coreutils bottle, then run:
$ ln -s /var/log/cups /tmp/linkeddir # symlink to another directory
$ greadlink -f /tmp/linkeddir/.. # canonical path of the link parent
/private/var/log
Note that readlink -f has resolved /tmp/linkeddir before resolving the .. parent dir reference. Of course, there is no readlink -f on Mac either.
So as part of the a bash implementation for realpath I re-implemented what a GNUlib canonicalize_filename_mode(path, CAN_ALL_BUT_LAST) function call does, in Bash 3.2; this is also the function call that GNU readlink -f makes:
# shellcheck shell=bash
set -euo pipefail
_contains() {
# return true if first argument is present in the other arguments
local elem value
value="$1"
shift
for elem in "$@"; do
if [[ $elem == "$value" ]]; then
return 0
fi
done
return 1
}
_canonicalize_filename_mode() {
# resolve any symlink targets, GNU readlink -f style
# where every path component except the last should exist and is
# resolved if it is a symlink. This is essentially a re-implementation
# of canonicalize_filename_mode(path, CAN_ALL_BUT_LAST).
# takes the path to canonicalize as first argument
local path result component seen
seen=()
path="$1"
result="/"
if [[ $path != /* ]]; then # add in current working dir if relative
result="$PWD"
fi
while [[ -n $path ]]; do
component="${path%%/*}"
case "$component" in
'') # empty because it started with /
path="${path:1}" ;;
.) # ./ current directory, do nothing
path="${path:1}" ;;
..) # ../ parent directory
if [[ $result != "/" ]]; then # not at the root?
result="${result%/*}" # then remove one element from the path
fi
path="${path:2}" ;;
*)
# add this component to the result, remove from path
if [[ $result != */ ]]; then
result="$result/"
fi
result="$result$component"
path="${path:${#component}}"
# element must exist, unless this is the final component
if [[ $path =~ [^/] && ! -e $result ]]; then
echo "$1: No such file or directory" >&2
return 1
fi
# if the result is a link, prefix it to the path, to continue resolving
if [[ -L $result ]]; then
if _contains "$result" "${seen[@]+"${seen[@]}"}"; then
# we've seen this link before, abort
echo "$1: Too many levels of symbolic links" >&2
return 1
fi
seen+=("$result")
path="$(readlink "$result")$path"
if [[ $path = /* ]]; then
# if the link is absolute, restart the result from /
result="/"
elif [[ $result != "/" ]]; then
# otherwise remove the basename of the link from the result
result="${result%/*}"
fi
elif [[ $path =~ [^/] && ! -d $result ]]; then
# otherwise all but the last element must be a dir
echo "$1: Not a directory" >&2
return 1
fi
;;
esac
done
echo "$result"
}
It includes circular symlink detection, exiting if the same (intermediary) path is seen twice.
If all you need is readlink -f, then you can use the above as:
readlink() {
if [[ $1 != -f ]]; then # poor-man's option parsing
# delegate to the standard readlink command
command readlink "$@"
return
fi
local path result seenerr
shift
seenerr=
for path in "$@"; do
# by default readlink suppresses error messages
if ! result=$(_canonicalize_filename_mode "$path" 2>/dev/null); then
seenerr=1
continue
fi
echo "$result"
done
if [[ $seenerr ]]; then
return 1;
fi
}
For realpath, I also needed --relative-to and --relative-base support, which give you relative paths after canonicalizing:
_realpath() {
# GNU realpath replacement for bash 3.2 (OS X)
# accepts --relative-to= and --relative-base options
# and produces canonical (relative or absolute) paths for each
# argument on stdout, errors on stderr, and returns 0 on success
# and 1 if at least 1 path triggered an error.
local relative_to relative_base seenerr path
relative_to=
relative_base=
seenerr=
while [[ $# -gt 0 ]]; do
case $1 in
"--relative-to="*)
relative_to=$(_canonicalize_filename_mode "${1#*=}")
shift 1;;
"--relative-base="*)
relative_base=$(_canonicalize_filename_mode "${1#*=}")
shift 1;;
*)
break;;
esac
done
if [[
-n $relative_to
&& -n $relative_base
&& ${relative_to#${relative_base}/} == "$relative_to"
]]; then
# relative_to is not a subdir of relative_base -> ignore both
relative_to=
relative_base=
elif [[ -z $relative_to && -n $relative_base ]]; then
# if relative_to has not been set but relative_base has, then
# set relative_to from relative_base, simplifies logic later on
relative_to="$relative_base"
fi
for path in "$@"; do
if ! real=$(_canonicalize_filename_mode "$path"); then
seenerr=1
continue
fi
# make path relative if so required
if [[
-n $relative_to
&& ( # path must not be outside relative_base to be made relative
-z $relative_base || ${real#${relative_base}/} != "$real"
)
]]; then
local common_part parentrefs
common_part="$relative_to"
parentrefs=
while [[ ${real#${common_part}/} == "$real" ]]; do
common_part="$(dirname "$common_part")"
parentrefs="..${parentrefs:+/$parentrefs}"
done
if [[ $common_part != "/" ]]; then
real="${parentrefs:+${parentrefs}/}${real#${common_part}/}"
fi
fi
echo "$real"
done
if [[ $seenerr ]]; then
return 1
fi
}
if ! command -v realpath > /dev/null 2>&1; then
# realpath is not available on OSX unless you install the `coreutils` brew
realpath() { _realpath "$@"; }
fi
I included unit tests in my Code Review request for this code.
Based on the communication with commenter, I agreed that it is very hard and has no trival way to implement a realpath behaves totally same as Ubuntu.
But the following version, can handle corner cases best answer can't and satisfy my daily needs on macbook. Put this code into your ~/.bashrc and remember:
# 1. if is a dir, try cd and pwd
# 2. if is a file, try cd its parent and concat dir+file
realpath() {
[ "$1" = "" ] && return 1
dir=`dirname "$1"`
file=`basename "$1"`
last=`pwd`
[ -d "$dir" ] && cd $dir || return 1
if [ -d "$file" ];
then
# case 1
cd $file && pwd || return 1
else
# case 2
echo `pwd`/$file | sed 's/\/\//\//g'
fi
cd $last
}
$( cd "$(dirname "$0")" ; pwd -P )– Jason Sbrew install coreutils– Vojtěch