Related
The GNU version of rm has a cool -I flag. From the manpage:
-I prompt once before removing more than three files, or when removing recursively. Less
intrusive than -i, while still giving protection against most mistakes
Macs don't:
$ rm -I scratch
rm: illegal option -- I
usage: rm [-f | -i] [-dPRrvW] file ...
unlink file
Sometimes people have coreutils (the GNU version) installed on Macs and sometimes they don't. Is there a way to detect this command line flag before proceeding? I'd like to have something like this in my bash_profile:
if [ has_gnu_rm_version ]; then
alias rm="rm -I"
fi
strings /bin/rm | grep -q 'GNU coreutils'
if $? is 0, it is coreutils
I would recommend not starting down this road at all. Target your scripts to be as portable as possible, and only rely on flags/options/behaviors you can count on. Shell scripting is hard enough - why add more room for error?
To get a sense of the kind of thing I have in mind, check out Ryan Tomayko's Shell Haters talk. He also has a very well-organized page with links to POSIX descriptions of shell features and utilities. Here's rm, for example.
I'd say test the output of rm -I on a temp file, if it passes then use the alias
touch /tmp/my_core_util_check
if rm -I /tmp/my_core_util_check > /dev/null 2>&1 ; then
alias rm="rm -I"
else
rm /tmp/my_core_util_check;
fi
You could always ask rm its version with --version and check to see if it says gnu or coreutils like this:
rm --version 2>&1 | grep -i gnu &> /dev/null
[ $? -eq 0 ] && alias rm="rm -I"
how about something like this?
#!/bin/bash
rm -I &> /dev/null
if [ "$?" == "0" ]; then
echo coreutils detected
else
echo bsd version detected
fi
Suppose I have a simple makefile like:
hello:
echo "hello world"
bye:
echo "bye bye"
Then in bash I want something like:
make h < tab >
so it can complete to
make hello
I found a simple way like creating empty files hello and bye but I'm looking for something more sophisticated.
Add this in your ~/.bash_profile file or ~/.bashrc file
complete -W "\`grep -oE '^[a-zA-Z0-9_.-]+:([^=]|$)' ?akefile | sed 's/[^a-zA-Z0-9_.-]*$//'\`" make
This searches for a target in your Makefile titled 'Makefile' or 'makefile' (note the capital ? wildcard in ?akefile) using grep, and pipes it over to the complete command in bash which is used to specify how arguments are autocompleted. The -W flag denotes that the input to the complete command will be a wordlist which is accomplished by passing the results of grep through sed which arranges it into the desirable wordlist format.
Caveats and gotchas:
Your make file is named 'GNUMakefile' or anything else other than 'Makefile' or 'makefile'. If you frequently encounter such titles consider changing the regular expression ?akefile accordingly.
Forgetting to source your ~/.bash_profile or ~/.bashrc file after making the changes. I add this seemingly trivial detail since, to the uninitiated it is unfamiliar.
For any change to your bash files to take effect, source them using the command
source ~/.bashrc
or
source ~/.bash_profile
PS. You also now have the added ability to display the possible make targets by pressing [Tab] twice just like in bash completion. Just make sure you add a space after the command make before typing [Tab] twice.
This answer from 2010 is outdated - the project mentioned here seems to have been discontinued.
Could this be what you're looking for?
http://freshmeat.net/projects/bashcompletion/
make [Tab] would complete on all
targets in Makefile. This project was
conceived to produce programmable
completion routines for the most
common Linux/UNIX commands, reducing
the amount of typing sysadmins and
programmers need to do on a daily
basis.
There's a useful package called bash-completion available for most every OS. It includes Makefile completion.
(If you're using macOS and Homebrew, you can get this via brew install bash-completion.)
This seems to be default in at least Debian Lenny:
$ grep Makefile /etc/bash_completion
# make reads `GNUmakefile', then `makefile', then `Makefile'
elif [ -f ${makef_dir}/Makefile ]; then
makef=${makef_dir}/Makefile
# before we scan for targets, see if a Makefile name was
# deal with included Makefiles
The header of this file states:
# The latest version of this software can be obtained here:
#
# http://bash-completion.alioth.debian.org/
#
# RELEASE: 20080617.5
Here is a completion script that looks at the .PHONY: declaration.
_make_phony_words() {
local opt_revert
if [ -n "${BASH_VERSION:-}" ]; then
shopt -q nullglob || {
opt_revert=1 ; shopt -s nullglob ;
}
elif [ -n "${ZSH_VERSION:-}" ]; then
[[ -o nullglob ]] || {
opt_revert=1 ; setopt nullglob
}
fi
for f in ./?akefile ./*.make ; do
sed -nEe '/^.PHONY/ { s/^.PHONY:[ ]?// ; p ; } ' "$f" | tr ' ' $'\n' | sort -u
done
if [ -n "$opt_revert" ]; then
[ -n "${ZSH_VERSION:-}" ] && unsetopt nullglob
[ -n "${BASH_VERSION:-}" ] && shopt -u nullglob
fi
unset opt_revert
}
_make_phony_complete() {
local cur="${COMP_WORDS[COMP_CWORD]}"
COMPREPLY+=( $(compgen -W "$( _make_phony_words )" -- ${cur}) )
}
complete -F _make_phony_complete make
Makefile completion on steroids!
I had 2 problems with the normal completions:
Problem #1
Sometimes you have targets you want to call like make greet:hi and make greet:hola sort of like namespacing Makefile target names. So your Makefile ends up looking like:
greet\:hola:
echo "hola world"
# OR a .PHONY target
.PHONY: greet\:hi
greet\:hi:
echo "hi world"
In this case the auto-completions after : don't show up as it uses \: in the Makefile as shown above.
Problem #2
There wasn't a way to navigate through the list of all Makefile targets that match my input using arrow keys (or CTRL-p / CTRL-n) in my bash shell.
Basically, I wanted to use fuzzy search like approach on the targets (i.e. fzf).
FZF Repo: https://github.com/junegunn/fzf
Solution
Install FZF Dependency
Using Homebrew
You can use Homebrew (on macOS or Linux)
to install fzf.
brew install fzf
$(brew --prefix)/opt/fzf/install
Using Linux package managers
Package Manager
Linux Distribution
Command
APK
Alpine Linux
sudo apk add fzf
APT
Debian 9+/Ubuntu 19.10+
sudo apt-get install fzf
Conda
conda install -c conda-forge fzf
DNF
Fedora
sudo dnf install fzf
Nix
NixOS, etc.
nix-env -iA nixpkgs.fzf
Pacman
Arch Linux
sudo pacman -S fzf
pkg
FreeBSD
pkg install fzf
pkgin
NetBSD
pkgin install fzf
pkg_add
OpenBSD
pkg_add fzf
XBPS
Void Linux
sudo xbps-install -S fzf
Zypper
openSUSE
sudo zypper install fzf
FZF and : compatible auto-complete command
Put this in your .bashrc
complete -W "\`grep -oE '^[a-zA-Z0-9_.-]+[\\:]*[a-zA-Z0-9_.-]+:([^=]|$)' ?akefile | sort | uniq | sed 's/[^a-zA-Z0-9_.-]*$//' | sed 's/[\]//g' | fzf\`" make
Now just typing make and then hitting the key will work!
DEMO: in action!
Then you can use as following:
make using fzf
I added so I follow "include" directives in Makefile. So my .bashrc looks like this:
function followMakefile() {
grep -oE '^[a-zA-Z0-9_.-]+:([^=]|$)' ?akefile | sed 's/[^a-zA-Z0-9_.-]*$//'
for x in `grep -E '^include' ?akefile | sed 's/include //'`
do
grep -oE '^[a-zA-Z0-9_.-]+:([^=]|$)' $x | sed 's/[^a-zA-Z0-9_.-]*$//'
done
}
complete -W "\`followMakefile\`" make
In Ubuntu 10.04, source the following file:
. /etc/bash_completion
or uncomment it in
/etc/bash.bashrc
How can I find out where an alias is defined on my system? I am referring to the kind of alias that is used within a Terminal session launched from Mac OS X (10.6.3).
For example, if I enter the alias command with no parameters at a Terminal command prompt, I get a list of aliases that I have set, for example:
alias mysql='/usr/local/mysql/bin/mysql'
However, I have searched all over my system using Spotlight and mdfind in various startup files and so far can not find where this alias has been defined. ( I did it a long time ago and didn't write down where I assigned the alias).
For OSX, this 2-step sequence worked well for me, in locating an alias I'd created long ago and couldn't locate in expected place (~/.zshrc).
cweekly:~ $ which la
la: aliased to ls -lAh
cweekly:~$ grep -r ' ls -lAh' ~
/Users/cweekly//.oh-my-zsh/lib/aliases.zsh:alias la='ls -lAh'
Aha! "Hiding" in ~/.oh-my-zsh/lib/aliases.zsh. I had poked around a bit in .oh-my-zsh but had overlooked lib/aliases.zsh.
you can just simply type in alias on the command prompt to see what aliases you have. Otherwise, you can do a find on the most common places where aliases are defined, eg
grep -RHi "alias" /etc /root
First use the following commands
List all functions
functions
List all aliases
alias
If you aren't finding the alias or function consider a more aggressive searching method
Bash version
bash -ixlc : 2>&1 | grep thingToSearchHere
Zsh version
zsh -ixc : 2>&1 | grep thingToSearchHere
Brief Explanation of Options
-i Force shell to be interactive.
-c Take the first argument as a command to execute
-x -- equivalent to --xtrace
-l Make bash act as if invoked as a login shell
Also in future these are the standard bash config files
/etc/profile
~/.bash_profile or ~/.bash_login or ~/.profile
~/.bash_logout
~/.bashrc
More info: http://www.heimhardt.com/htdocs/bashrcs.html
A bit late to the party, but I was having the same problem (trying to find where the "l." command was aliased in RHEL6), and ended up in a place not mentioned in the previous answers. It may not be found in all bash implementations, but if the /etc/profile.d/ directory exists, try grepping there for unexplained aliases. That's where I found:
[user#server ~]$ grep l\\. /etc/profile.d/*
/etc/profile.d/colorls.csh:alias l. 'ls -d .*'
/etc/profile.d/colorls.csh:alias l. 'ls -d .* --color=auto'
/etc/profile.d/colorls.sh: alias l.='ls -d .*' 2>/dev/null
/etc/profile.d/colorls.sh:alias l.='ls -d .* --color=auto' 2>/dev/null
The directory isn't mentioned in the bash manpage, and isn't properly part of where bash searches for profile/startup info, but in the case of RHEL you can see the calling code within /etc/profile:
for i in /etc/profile.d/*.sh ; do
if [ -r "$i" ]; then
if [ "${-#*i}" != "$-" ]; then
. "$i"
else
. "$i" >/dev/null 2>&1
fi
fi
done
Please do check custom installations/addons/plugins you have added, in addition to the .zshrc/.bashrc/.profile etc files
So for me: it was git aliased to 'g'.
$ which g
g: aliased to git
Then I ran the following command to list all aliases
$ alias
I found a whole lot of git related aliases that I knew I had not manually added.
This got me thinking about packages or configurations I had installed. And so went to the
.oh-my-zsh
directory. Here I ran the following command:
$ grep -r 'git' . |grep -i alias
And lo and behold, I found my alias in :
./plugins/git/git.plugin.zsh
I found the answer ( I had been staring at the correct file but missed the obvious ).
The aliases in my case are defined in the file ~/.bash_profile
Somehow this eluded me.
For more complex setups (e.g. when you're using a shell script framework like bash-it, oh-my-zsh or the likes) it's often useful to add 'alias mysql' at key positions in your scripts. This will help you figure out exactly when the alias is added.
e.g.:
echo "before sourcing .bash-it:"
alias mysql
. $HOME/.bash-it/bash-it.sh
echo "after sourcing bash:"
alias mysql
I think that maybe this is similar to what ghostdog74 meant however their command didn't work for me.
I would try something like this:
for i in `find . -type f`; do # find all files in/under current dir
echo "========"
echo $i # print file name
cat $i | grep "alias" # find if it has alias and if it does print the line containing it
done
If you wanted to be really fancy you could even add an if [[ grep -c "alias" ]] then <print file name>
The only reliable way of finding where the alias could have been defined is by analyzing the list of files opened by bash using dtruss.
If
$ csrutil status
System Integrity Protection status: enabled.
you won't be able to open bash and you may need a copy.
$ cp /bin/bash mybash
$ $ codesign --remove-signature mybash
and then use
sudo dtruss -t open ./mybash -ic exit 2>&1 | awk -F'"' '/^open/ {print substr($2, 0, length($2)-2)}'
to list all the files where the alias could have been defined, like
/dev/dtracehelper
/dev/tty
/usr/share/locale/en_CA.UTF-8/LC_MESSAGES/BASH.mo
/usr/share/locale/en_CA.utf8/LC_MESSAGES/BASH.mo
/usr/share/locale/en_CA/LC_MESSAGES/BASH.mo
/usr/share/locale/en.UTF-8/LC_MESSAGES/BASH.mo
/usr/share/locale/en.utf8/LC_MESSAGES/BASH.mo
/usr/share/locale/en/LC_MESSAGES/BASH.mo
/Users/user/.bashrc
/Users/user/.bash_aliases
/Users/user/.bash_history
...
Try: alias | grep name_of_alias
Ex.: alias | grep mysql
or, as already mentioned above
which name_of_alias
In my case, I use Oh My Zsh, so I put aliases definition in ~/.zshrc file.
Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers.
This question does not appear to be about a specific programming problem, a software algorithm, or software tools primarily used by programmers. If you believe the question would be on-topic on another Stack Exchange site, you can leave a comment to explain where the question may be able to be answered.
Closed last year.
The community reviewed whether to reopen this question last year and left it closed:
Original close reason(s) were not resolved
Improve this question
On Linux, the readlink utility accepts an option -f that follows additional links. This doesn't seem to work on Mac and possibly BSD based systems. What would the equivalent be?
Here's some debug information:
$ which readlink; readlink -f
/usr/bin/readlink
readlink: illegal option -f
usage: readlink [-n] [file ...]
MacPorts and Homebrew provide a coreutils package containing greadlink (GNU readlink). Credit to Michael Kallweitt post in mackb.com.
brew install coreutils
greadlink -f file.txt
readlink -f does two things:
It iterates along a sequence of symlinks until it finds an actual file.
It returns that file's canonicalized name—i.e., its absolute pathname.
If you want to, you can just build a shell script that uses vanilla readlink behavior to achieve the same thing. Here's an example. Obviously you could insert this in your own script where you'd like to call readlink -f
#!/bin/sh
TARGET_FILE=$1
cd `dirname $TARGET_FILE`
TARGET_FILE=`basename $TARGET_FILE`
# Iterate down a (possible) chain of symlinks
while [ -L "$TARGET_FILE" ]
do
TARGET_FILE=`readlink $TARGET_FILE`
cd `dirname $TARGET_FILE`
TARGET_FILE=`basename $TARGET_FILE`
done
# Compute the canonicalized name by finding the physical path
# for the directory we're in and appending the target file.
PHYS_DIR=`pwd -P`
RESULT=$PHYS_DIR/$TARGET_FILE
echo $RESULT
Note that this doesn't include any error handling. Of particular importance, it doesn't detect symlink cycles. A simple way to do this would be to count the number of times you go around the loop and fail if you hit an improbably large number, such as 1,000.
EDITED to use pwd -P instead of $PWD.
Note that this script expects to be called like ./script_name filename, no -f, change $1 to $2 if you want to be able to use with -f filename like GNU readlink.
You may be interested in realpath(3), or Python's os.path.realpath. The two aren't exactly the same; the C library call requires that intermediary path components exist, while the Python version does not.
$ pwd
/tmp/foo
$ ls -l
total 16
-rw-r--r-- 1 miles wheel 0 Jul 11 21:08 a
lrwxr-xr-x 1 miles wheel 1 Jul 11 20:49 b -> a
lrwxr-xr-x 1 miles wheel 1 Jul 11 20:49 c -> b
$ python -c 'import os,sys;print(os.path.realpath(sys.argv[1]))' c
/private/tmp/foo/a
I know you said you'd prefer something more lightweight than another scripting language, but just in case compiling a binary is insufferable, you can use Python and ctypes (available on Mac OS X 10.5) to wrap the library call:
#!/usr/bin/python
import ctypes, sys
libc = ctypes.CDLL('libc.dylib')
libc.realpath.restype = ctypes.c_char_p
libc.__error.restype = ctypes.POINTER(ctypes.c_int)
libc.strerror.restype = ctypes.c_char_p
def realpath(path):
buffer = ctypes.create_string_buffer(1024) # PATH_MAX
if libc.realpath(path, buffer):
return buffer.value
else:
errno = libc.__error().contents.value
raise OSError(errno, "%s: %s" % (libc.strerror(errno), buffer.value))
if __name__ == '__main__':
print realpath(sys.argv[1])
Ironically, the C version of this script ought to be shorter. :)
A simple one-liner in perl that's sure to work almost everywhere without any external dependencies:
perl -MCwd -e 'print Cwd::abs_path shift' ~/non-absolute/file
Will dereference symlinks.
Usage in a script could be like this:
readlinkf(){ perl -MCwd -e 'print Cwd::abs_path shift' "$1";}
ABSPATH="$(readlinkf ./non-absolute/file)"
You might need both a portable, pure shell implementation, and unit-test coverage, as the number of edge-cases for something like this is non-trivial.
See my project on Github for tests and full code. What follows is a synopsis of the implementation:
As Keith Smith astutely points out, readlink -f does two things: 1) resolves symlinks recursively, and 2) canonicalizes the result, hence:
realpath() {
canonicalize_path "$(resolve_symlinks "$1")"
}
First, the symlink resolver implementation:
resolve_symlinks() {
local dir_context path
path=$(readlink -- "$1")
if [ $? -eq 0 ]; then
dir_context=$(dirname -- "$1")
resolve_symlinks "$(_prepend_path_if_relative "$dir_context" "$path")"
else
printf '%s\n' "$1"
fi
}
_prepend_path_if_relative() {
case "$2" in
/* ) printf '%s\n' "$2" ;;
* ) printf '%s\n' "$1/$2" ;;
esac
}
Note that this is a slightly simplified version of the full implementation. The full implementation adds a small check for symlink cycles, as well as massages the output a bit.
Finally, the function for canonicalizing a path:
canonicalize_path() {
if [ -d "$1" ]; then
_canonicalize_dir_path "$1"
else
_canonicalize_file_path "$1"
fi
}
_canonicalize_dir_path() {
(cd "$1" 2>/dev/null && pwd -P)
}
_canonicalize_file_path() {
local dir file
dir=$(dirname -- "$1")
file=$(basename -- "$1")
(cd "$dir" 2>/dev/null && printf '%s/%s\n' "$(pwd -P)" "$file")
}
That's it, more or less. Simple enough to paste into your script, but tricky enough that you'd be crazy to rely on any code that doesn't have unit tests for your use cases.
Install homebrew
Run "brew install coreutils"
Run "greadlink -f path"
greadlink is the gnu readlink that implements -f. You can use macports or others as well, I prefer homebrew.
I made a script called realpath personally which looks a little something like:
#!/usr/bin/env python
import os, sys
print(os.path.realpath(sys.argv[1]))
What about this?
function readlink() {
DIR="${1%/*}"
(cd "$DIR" && echo "$(pwd -P)")
}
A lazy way that works for me,
$ brew install coreutils
$ ln -s /usr/local/bin/greadlink /usr/local/bin/readlink
$ which readlink
/usr/local/bin/readlink
/usr/bin/readlink
Implementation
Install brew
Follow the instructions at https://brew.sh/
Install the coreutils package
brew install coreutils
Create an Alias or Symlink
3a. Create an an alias (per user)
You can place your alias in ~/.bashrc, ~/.bash_profile, or wherever you are used to keeping your bash aliases. I personally keep mine in ~/.bashrc
alias readlink=greadlink
3b. Create a symbolic link (system wide)
ln -s /usr/local/bin/greadlink /usr/local/bin/readlink (credit: Izana)
This will create a symbolic link in /usr/local/bin while keeping the original readlink binary in tact. It works because the search for readlink will return 2 results. But the second in /usr/local/bin will take precedence.
e.g. which readlink
To undo this change simply unlink /usr/local/bin/readlink
Additional Tools
You can create similar aliases or symlinks for other coreutils such as gmv, gdu, gdf, and so on. But beware that the GNU behavior on a mac machine may be confusing to others used to working with native coreutils, or may behave in unexpected ways on your mac system.
Explanation
coreutils is a brew package that installs GNU/Linux core utilities which correspond to the Mac OSX implementation of them so that you can use those
You may find programs or utilties on your mac osx system which seem similar to Linux coreutils ("Core Utilities") yet they differ in some ways (such as having different flags).
This is because the Mac OSX implementation of these tools are different. To get the original GNU/Linux-like behavior you can install the coreutils package via the brew package management system.
This will install corresponding core utilities, prefixed by g. E.g. for readlink, you will find a corresponding greadlink program.
In order to make readlink perform like the GNU readlink (greadlink) implementation, you can create a simple alias or symbolic link after you install coreutils.
FreeBSD and OSX have a version of statderived from NetBSD.
You can adjust the output with format switches (see the manual pages at the links above).
% cd /service
% ls -tal
drwxr-xr-x 22 root wheel 27 Aug 25 10:41 ..
drwx------ 3 root wheel 8 Jun 30 13:59 .s6-svscan
drwxr-xr-x 3 root wheel 5 Jun 30 13:34 .
lrwxr-xr-x 1 root wheel 30 Dec 13 2013 clockspeed-adjust -> /var/service/clockspeed-adjust
lrwxr-xr-x 1 root wheel 29 Dec 13 2013 clockspeed-speed -> /var/service/clockspeed-speed
% stat -f%R clockspeed-adjust
/var/service/clockspeed-adjust
% stat -f%Y clockspeed-adjust
/var/service/clockspeed-adjust
Some OS X versions of stat may lack the -f%R option for formats. In this case -stat -f%Y may suffice. The -f%Y option will show the target of a symlink, whereas -f%R shows the absolute pathname corresponding to the file.
EDIT:
If you're able to use Perl (Darwin/OS X comes installed with recent verions of perl) then:
perl -MCwd=abs_path -le 'print abs_path readlink(shift);' linkedfile.txt
will work.
The easiest way to solve this problem and enable the functionality of readlink on Mac w/ Homebrew installed or FreeBSD is to install 'coreutils' package. May also be necessary on certain Linux distributions and other POSIX OS.
For example, in FreeBSD 11, I installed by invoking:
# pkg install coreutils
On MacOS with Homebrew, the command would be:
$ brew install coreutils
Not really sure why the other answers are so complicated, that's all there is to it. The files aren't in a different place, they're just not installed yet.
Here is a portable shell function that should work in ANY Bourne comparable shell.
It will resolve the relative path punctuation ".. or ." and dereference symbolic links.
If for some reason you do not have a realpath(1) command, or readlink(1) this can be aliased.
which realpath || alias realpath='real_path'
Enjoy:
real_path () {
OIFS=$IFS
IFS='/'
for I in $1
do
# Resolve relative path punctuation.
if [ "$I" = "." ] || [ -z "$I" ]
then continue
elif [ "$I" = ".." ]
then FOO="${FOO%%/${FOO##*/}}"
continue
else FOO="${FOO}/${I}"
fi
## Resolve symbolic links
if [ -h "$FOO" ]
then
IFS=$OIFS
set `ls -l "$FOO"`
while shift ;
do
if [ "$1" = "->" ]
then FOO=$2
shift $#
break
fi
done
IFS='/'
fi
done
IFS=$OIFS
echo "$FOO"
}
also, just in case anybody is interested here is how to implement basename and dirname in 100% pure shell code:
## http://www.opengroup.org/onlinepubs/000095399/functions/dirname.html
# the dir name excludes the least portion behind the last slash.
dir_name () {
echo "${1%/*}"
}
## http://www.opengroup.org/onlinepubs/000095399/functions/basename.html
# the base name excludes the greatest portion in front of the last slash.
base_name () {
echo "${1##*/}"
}
You can find updated version of this shell code at my google site: http://sites.google.com/site/jdisnard/realpath
EDIT:
This code is licensed under the terms of the 2-clause (freeBSD style) license.
A copy of the license may be found by following the above hyperlink to my site.
Begin Update
This is such a frequent problem that we have put together a Bash 4 library for free use (MIT License) called realpath-lib. This is designed to emulate readlink -f by default and includes two test suites to verify (1) that it works for a given unix system and (2) against readlink -f if installed (but this is not required). Additionally, it can be used to investigate, identify and unwind deep, broken symlinks and circular references, so it can be a useful tool for diagnosing deeply-nested physical or symbolic directory and file problems. It can be found at github.com or bitbucket.org.
End Update
Another very compact and efficient solution that does not rely on anything but Bash is:
function get_realpath() {
[[ ! -f "$1" ]] && return 1 # failure : file does not exist.
[[ -n "$no_symlinks" ]] && local pwdp='pwd -P' || local pwdp='pwd' # do symlinks.
echo "$( cd "$( echo "${1%/*}" )" 2>/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. As long as no_symlinks is set to something, ie no_symlinks='on' then symlinks will be resolved to the physical system. Otherwise they will be applied (the default setting).
This should work on any system that provides Bash, and will return a Bash compatible exit code for testing purposes.
There are already a lot of answers, but none worked for me... So this is what I'm using now.
readlink_f() {
local target="$1"
[ -f "$target" ] || return 1 #no nofile
while [ -L "$target" ]; do
target="$(readlink "$target")"
done
echo "$(cd "$(dirname "$target")"; pwd -P)/$target"
}
Since my work is used by people with non-BSD Linux as well as macOS, I've opted for using these aliases in our build scripts (sed included since it has similar issues):
##
# If you're running macOS, use homebrew to install greadlink/gsed first:
# brew install coreutils
#
# Example use:
# # Gets the directory of the currently running script
# dotfilesDir=$(dirname "$(globalReadlink -fm "$0")")
# alias al='pico ${dotfilesDir}/aliases.local'
##
function globalReadlink () {
# Use greadlink if on macOS; otherwise use normal readlink
if [[ $OSTYPE == darwin* ]]; then
greadlink "$#"
else
readlink "$#"
fi
}
function globalSed () {
# Use gsed if on macOS; otherwise use normal sed
if [[ $OSTYPE == darwin* ]]; then
gsed "$#"
else
sed "$#"
fi
}
Optional check you could add to automatically install homebrew + coreutils dependencies:
if [[ "$OSTYPE" == "darwin"* ]]; then
# Install brew if needed
if [ -z "$(which brew)" ]; then
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)";
fi
# Check for coreutils
if [ -z "$(brew ls coreutils)" ]; then
brew install coreutils
fi
fi
I suppose to be truly "global" it needs to check others...but that probably comes close to the 80/20 mark.
POSIX compliant readlink -f implementation for POSIX shell scripts
https://github.com/ko1nksm/readlinkf
This is POSIX compliant (no bashism). It uses neither readlink nor realpath. I have verified that it is exactly the same by comparing with GNU readlink -f (see test results). It has error handling and good performance. You can safely replace from readlink -f. The license is CC0, so you can use it for any project.
This code is adopted in the bats-core project.
# POSIX compliant version
readlinkf_posix() {
[ "${1:-}" ] || return 1
max_symlinks=40
CDPATH='' # to avoid changing to an unexpected directory
target=$1
[ -e "${target%/}" ] || target=${1%"${1##*[!/]}"} # trim trailing slashes
[ -d "${target:-/}" ] && target="$target/"
cd -P . 2>/dev/null || return 1
while [ "$max_symlinks" -ge 0 ] && max_symlinks=$((max_symlinks - 1)); do
if [ ! "$target" = "${target%/*}" ]; then
case $target in
/*) cd -P "${target%/*}/" 2>/dev/null || break ;;
*) cd -P "./${target%/*}" 2>/dev/null || break ;;
esac
target=${target##*/}
fi
if [ ! -L "$target" ]; then
target="${PWD%/}${target:+/}${target}"
printf '%s\n' "${target:-/}"
return 0
fi
# `ls -dl` format: "%s %u %s %s %u %s %s -> %s\n",
# <file mode>, <number of links>, <owner name>, <group name>,
# <size>, <date and time>, <pathname of link>, <contents of link>
# https://pubs.opengroup.org/onlinepubs/9699919799/utilities/ls.html
link=$(ls -dl -- "$target" 2>/dev/null) || break
target=${link#*" $target -> "}
done
return 1
}
Please refer to the latest code. It may some fixed.
Better late than never, I suppose. I was motivated to develop this specifically because my Fedora scripts weren't working on the Mac. The problem is dependencies and Bash. Macs don't have them, or if they do, they are often somewhere else (another path). Dependency path manipulation in a cross-platform Bash script is a headache at best and a security risk at worst - so it's best to avoid their use, if possible.
The function get_realpath() below is simple, Bash-centric, and no dependencies are required. I uses only the Bash builtins echo and cd. It is also fairly secure, as everything gets tested at each stage of the way and it returns error conditions.
If you don't want to follow symlinks, then put set -P at the front of the script, but otherwise cd should resolve the symlinks by default. It's been tested with file arguments that are {absolute | relative | symlink | local} and it returns the absolute path to the file. So far we've not had any problems with it.
function get_realpath() {
if [[ -f "$1" ]]
then
# file *must* exist
if cd "$(echo "${1%/*}")" &>/dev/null
then
# file *may* not be local
# exception is ./file.ext
# try 'cd .; cd -;' *works!*
local tmppwd="$PWD"
cd - &>/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
}
You can combine this with other functions get_dirname, get_filename, get_stemname and validate_path. These can be found at our GitHub repository as realpath-lib (full disclosure - this is our product but we offer it free to the community without any restrictions). It also could serve as a instructional tool - it's well documented.
We've tried our best to apply so-called 'modern Bash' practices, but Bash is a big subject and I'm certain there will always be room for improvement. It requires Bash 4+ but could be made to work with older versions if they are still around.
echo $(cd $(dirname file1) ; pwd -P)
I wrote a realpath utility for OS X which can provide the same results as readlink -f.
Here is an example:
(jalcazar#mac tmp)$ ls -l a
lrwxrwxrwx 1 jalcazar jalcazar 11 8月 25 19:29 a -> /etc/passwd
(jalcazar#mac tmp)$ realpath a
/etc/passwd
If you are using MacPorts, you can install it with the following command: sudo port selfupdate && sudo port install realpath.
Truely platform-indpendent would be also this R-onliner
readlink(){ RScript -e "cat(normalizePath(commandArgs(T)[1]))" "$1";}
To actually mimic readlink -f <path>, $2 instead of $1 would need to be used.
I have simply pasted the following to the top of my bash scripts:
#!/usr/bin/env bash -e
declare script=$(basename "$0")
declare dirname=$(dirname "$0")
declare scriptDir
if [[ $(uname) == 'Linux' ]];then
# use readlink -f
scriptDir=$(readlink -f "$dirname")
else
# can't use readlink -f, do a pwd -P in the script directory and then switch back
if [[ "$dirname" = '.' ]];then
# don't change directory, we are already inside
scriptDir=$(pwd -P)
else
# switch to the directory and then switch back
pwd=$(pwd)
cd "$dirname"
scriptDir=$(pwd -P)
cd "$pwd"
fi
fi
And removed all instances of readlink -f. $scriptDir and $script then will be available for the rest of the script.
While this does not follow all symlinks, it works on all systems and appears to be good enough for most use cases, it switches the directory into the containing folder, and then it does a pwd -P to get the real path of that directory, and then finally switch back to the original.
Perl has a readlink function (e.g. How do I copy symbolic links in Perl?). This works across most platforms, including OS X:
perl -e "print readlink '/path/to/link'"
For example:
$ mkdir -p a/b/c
$ ln -s a/b/c x
$ perl -e "print readlink 'x'"
a/b/c
The answer from #Keith Smith gives an infinite loop.
Here is my answer, which i use only on SunOS (SunOS miss so much POSIX and GNU commands).
It's a script file you have to put in one of your $PATH directories:
#!/bin/sh
! (($#)) && echo -e "ERROR: readlink <link to analyze>" 1>&2 && exit 99
link="$1"
while [ -L "$link" ]; do
lastLink="$link"
link=$(/bin/ls -ldq "$link")
link="${link##* -> }"
link=$(realpath "$link")
[ "$link" == "$lastlink" ] && echo -e "ERROR: link loop detected on $link" 1>&2 && break
done
echo "$link"
This is what I use:
stat -f %N $your_path
The paths to readlink are different between my system and yours. Please try specifying the full path:
/sw/sbin/readlink -f
Given an absolute or relative path (in a Unix-like system), I would like to determine the full path of the target after resolving any intermediate symlinks. Bonus points for also resolving ~username notation at the same time.
If the target is a directory, it might be possible to chdir() into the directory and then call getcwd(), but I really want to do this from a shell script rather than writing a C helper. Unfortunately, shells have a tendency to try to hide the existence of symlinks from the user (this is bash on OS X):
$ ls -ld foo bar
drwxr-xr-x 2 greg greg 68 Aug 11 22:36 bar
lrwxr-xr-x 1 greg greg 3 Aug 11 22:36 foo -> bar
$ cd foo
$ pwd
/Users/greg/tmp/foo
$
What I want is a function resolve() such that when executed from the tmp directory in the above example, resolve("foo") == "/Users/greg/tmp/bar".
readlink -f "$path"
Editor's note: The above works with GNU readlink and FreeBSD/PC-BSD/OpenBSD readlink, but not on OS X as of 10.11.
GNU readlink offers additional, related options, such as -m for resolving a symlink whether or not the ultimate target exists.
Note since GNU coreutils 8.15 (2012-01-06), there is a realpath program available that is less obtuse and more flexible than the above. It's also compatible with the FreeBSD util of the same name. It also includes functionality to generate a relative path between two files.
realpath $path
[Admin addition below from comment by halloleo —danorton]
For Mac OS X (through at least 10.11.x), use readlink without the -f option:
readlink $path
Editor's note: This will not resolve symlinks recursively and thus won't report the ultimate target; e.g., given symlink a that points to b, which in turn points to c, this will only report b (and won't ensure that it is output as an absolute path).
Use the following perl command on OS X to fill the gap of the missing readlink -f functionality:
perl -MCwd -le 'print Cwd::abs_path(shift)' "$path"
According to the standards, pwd -P should return the path with symlinks resolved.
C function char *getcwd(char *buf, size_t size) from unistd.h should have the same behaviour.
getcwd
pwd
"pwd -P" seems to work if you just want the directory, but if for some reason you want the name of the actual executable I don't think that helps. Here's my solution:
#!/bin/bash
# get the absolute path of the executable
SELF_PATH=$(cd -P -- "$(dirname -- "$0")" && pwd -P) && SELF_PATH=$SELF_PATH/$(basename -- "$0")
# resolve symlinks
while [[ -h $SELF_PATH ]]; do
# 1) cd to directory of the symlink
# 2) cd to the directory of where the symlink points
# 3) get the pwd
# 4) append the basename
DIR=$(dirname -- "$SELF_PATH")
SYM=$(readlink "$SELF_PATH")
SELF_PATH=$(cd "$DIR" && cd "$(dirname -- "$SYM")" && pwd)/$(basename -- "$SYM")
done
One of my favorites is realpath foo
realpath - return the canonicalized absolute pathname
realpath expands all symbolic links and resolves references to '/./', '/../' and extra '/' characters in the null terminated string named by path and
stores the canonicalized absolute pathname in the buffer of size PATH_MAX named by resolved_path. The resulting path will have no symbolic link, '/./' or
'/../' components.
readlink -e [filepath]
seems to be exactly what you're asking for
- it accepts an arbirary path, resolves all symlinks, and returns the "real" path
- and it's "standard *nix" that likely all systems already have
Another way:
# Gets the real path of a link, following all links
myreadlink() { [ ! -h "$1" ] && echo "$1" || (local link="$(expr "$(command ls -ld -- "$1")" : '.*-> \(.*\)$')"; cd $(dirname $1); myreadlink "$link" | sed "s|^\([^/].*\)\$|$(dirname $1)/\1|"); }
# Returns the absolute path to a command, maybe in $PATH (which) or not. If not found, returns the same
whereis() { echo $1 | sed "s|^\([^/].*/.*\)|$(pwd)/\1|;s|^\([^/]*\)$|$(which -- $1)|;s|^$|$1|"; }
# Returns the realpath of a called command.
whereis_realpath() { local SCRIPT_PATH=$(whereis $1); myreadlink ${SCRIPT_PATH} | sed "s|^\([^/].*\)\$|$(dirname ${SCRIPT_PATH})/\1|"; }
Putting some of the given solutions together, knowing that readlink is available on most systems, but needs different arguments, this works well for me on OSX and Debian. I'm not sure about BSD systems. Maybe the condition needs to be [[ $OSTYPE != darwin* ]] to exclude -f from OSX only.
#!/bin/bash
MY_DIR=$( cd $(dirname $(readlink `[[ $OSTYPE == linux* ]] && echo "-f"` $0)) ; pwd -P)
echo "$MY_DIR"
Here's how one can get the actual path to the file in MacOS/Unix using an inline Perl script:
FILE=$(perl -e "use Cwd qw(abs_path); print abs_path('$0')")
Similarly, to get the directory of a symlinked file:
DIR=$(perl -e "use Cwd qw(abs_path); use File::Basename; print dirname(abs_path('$0'))")
Common shell scripts often have to find their "home" directory even if they are invoked as a symlink. The script thus have to find their "real" position from just $0.
cat `mvn`
on my system prints a script containing the following, which should be a good hint at what you need.
if [ -z "$M2_HOME" ] ; then
## resolve links - $0 may be a link to maven's home
PRG="$0"
# need this for relative symlinks
while [ -h "$PRG" ] ; do
ls=`ls -ld "$PRG"`
link=`expr "$ls" : '.*-> \(.*\)$'`
if expr "$link" : '/.*' > /dev/null; then
PRG="$link"
else
PRG="`dirname "$PRG"`/$link"
fi
done
saveddir=`pwd`
M2_HOME=`dirname "$PRG"`/..
# make it fully qualified
M2_HOME=`cd "$M2_HOME" && pwd`
Note: I believe this to be a solid, portable, ready-made solution, which is invariably lengthy for that very reason.
Below is a fully POSIX-compliant script / function that is therefore cross-platform (works on macOS too, whose readlink still doesn't support -f as of 10.12 (Sierra)) - it uses only POSIX shell language features and only POSIX-compliant utility calls.
It is a portable implementation of GNU's readlink -e (the stricter version of readlink -f).
You can run the script with sh or source the function in bash, ksh, and zsh:
For instance, inside a script you can use it as follows to get the running's script true directory of origin, with symlinks resolved:
trueScriptDir=$(dirname -- "$(rreadlink "$0")")
rreadlink script / function definition:
The code was adapted with gratitude from this answer.
I've also created a bash-based stand-alone utility version here, which you can install with
npm install rreadlink -g, if you have Node.js installed.
#!/bin/sh
# SYNOPSIS
# rreadlink <fileOrDirPath>
# DESCRIPTION
# Resolves <fileOrDirPath> to its ultimate target, if it is a symlink, and
# prints its canonical path. If it is not a symlink, its own canonical path
# is printed.
# A broken symlink causes an error that reports the non-existent target.
# LIMITATIONS
# - Won't work with filenames with embedded newlines or filenames containing
# the string ' -> '.
# COMPATIBILITY
# This is a fully POSIX-compliant implementation of what GNU readlink's
# -e option does.
# EXAMPLE
# In a shell script, use the following to get that script's true directory of origin:
# trueScriptDir=$(dirname -- "$(rreadlink "$0")")
rreadlink() ( # Execute the function in a *subshell* to localize variables and the effect of `cd`.
target=$1 fname= targetDir= CDPATH=
# Try to make the execution environment as predictable as possible:
# All commands below are invoked via `command`, so we must make sure that
# `command` itself is not redefined as an alias or shell function.
# (Note that command is too inconsistent across shells, so we don't use it.)
# `command` is a *builtin* in bash, dash, ksh, zsh, and some platforms do not
# even have an external utility version of it (e.g, Ubuntu).
# `command` bypasses aliases and shell functions and also finds builtins
# in bash, dash, and ksh. In zsh, option POSIX_BUILTINS must be turned on for
# that to happen.
{ \unalias command; \unset -f command; } >/dev/null 2>&1
[ -n "$ZSH_VERSION" ] && options[POSIX_BUILTINS]=on # make zsh find *builtins* with `command` too.
while :; do # Resolve potential symlinks until the ultimate target is found.
[ -L "$target" ] || [ -e "$target" ] || { command printf '%s\n' "ERROR: '$target' does not exist." >&2; return 1; }
command cd "$(command dirname -- "$target")" # Change to target dir; necessary for correct resolution of target path.
fname=$(command basename -- "$target") # Extract filename.
[ "$fname" = '/' ] && fname='' # !! curiously, `basename /` returns '/'
if [ -L "$fname" ]; then
# Extract [next] target path, which may be defined
# *relative* to the symlink's own directory.
# Note: We parse `ls -l` output to find the symlink target
# which is the only POSIX-compliant, albeit somewhat fragile, way.
target=$(command ls -l "$fname")
target=${target#* -> }
continue # Resolve [next] symlink target.
fi
break # Ultimate target reached.
done
targetDir=$(command pwd -P) # Get canonical dir. path
# Output the ultimate target's canonical path.
# Note that we manually resolve paths ending in /. and /.. to make sure we have a normalized path.
if [ "$fname" = '.' ]; then
command printf '%s\n' "${targetDir%/}"
elif [ "$fname" = '..' ]; then
# Caveat: something like /var/.. will resolve to /private (assuming /var# -> /private/var), i.e. the '..' is applied
# AFTER canonicalization.
command printf '%s\n' "$(command dirname -- "${targetDir}")"
else
command printf '%s\n' "${targetDir%/}/$fname"
fi
)
rreadlink "$#"
A tangent on security:
jarno, in reference to the function ensuring that builtin command is not shadowed by an alias or shell function of the same name, asks in a comment:
What if unalias or unset and [ are set as aliases or shell functions?
The motivation behind rreadlink ensuring that command has its original meaning is to use it to bypass (benign) convenience aliases and functions often used to shadow standard commands in interactive shells, such as redefining ls to include favorite options.
I think it's safe to say that unless you're dealing with an untrusted, malicious environment, worrying about unalias or unset - or, for that matter, while, do, ... - being redefined is not a concern.
There is something that the function must rely on to have its original meaning and behavior - there is no way around that.
That POSIX-like shells allow redefinition of builtins and even language keywords is inherently a security risk (and writing paranoid code is hard in general).
To address your concerns specifically:
The function relies on unalias and unset having their original meaning. Having them redefined as shell functions in a manner that alters their behavior would be a problem; redefinition as an alias is
not necessarily a concern, because quoting (part of) the command name (e.g., \unalias) bypasses aliases.
However, quoting is not an option for shell keywords (while, for, if, do, ...) and while shell keywords do take precedence over shell functions, in bash and zsh aliases have the highest precedence, so to guard against shell-keyword redefinitions you must run unalias with their names (although in non-interactive bash shells (such as scripts) aliases are not expanded by default - only if shopt -s expand_aliases is explicitly called first).
To ensure that unalias - as a builtin - has its original meaning, you must use \unset on it first, which requires that unset have its original meaning:
unset is a shell builtin, so to ensure that it is invoked as such, you'd have to make sure that it itself is not redefined as a function. While you can bypass an alias form with quoting, you cannot bypass a shell-function form - catch 22.
Thus, unless you can rely on unset to have its original meaning, from what I can tell, there is no guaranteed way to defend against all malicious redefinitions.
Is your path a directory, or might it be a file? If it's a directory, it's simple:
(cd "$DIR"; pwd -P)
However, if it might be a file, then this won't work:
DIR=$(cd $(dirname "$FILE"); pwd -P); echo "${DIR}/$(readlink "$FILE")"
because the symlink might resolve into a relative or full path.
On scripts I need to find the real path, so that I might reference configuration or other scripts installed together with it, I use this:
SOURCE="${BASH_SOURCE[0]}"
while [ -h "$SOURCE" ]; do # resolve $SOURCE until the file is no longer a symlink
DIR="$( cd -P "$( dirname "$SOURCE" )" && pwd )"
SOURCE="$(readlink "$SOURCE")"
[[ $SOURCE != /* ]] && SOURCE="$DIR/$SOURCE" # if $SOURCE was a relative symlink, we need to resolve it relative to the path where the symlink file was located
done
You could set SOURCE to any file path. Basically, for as long as the path is a symlink, it resolves that symlink. The trick is in the last line of the loop. If the resolved symlink is absolute, it will use that as SOURCE. However, if it is relative, it will prepend the DIR for it, which was resolved into a real location by the simple trick I first described.
function realpath {
local r=$1; local t=$(readlink $r)
while [ $t ]; do
r=$(cd $(dirname $r) && cd $(dirname $t) && pwd -P)/$(basename $t)
t=$(readlink $r)
done
echo $r
}
#example usage
SCRIPT_PARENT_DIR=$(dirname $(realpath "$0"))/..
In case where pwd can't be used (e.g. calling a scripts from a different location), use realpath (with or without dirname):
$(dirname $(realpath $PATH_TO_BE_RESOLVED))
Works both when calling through (multiple) symlink(s) or when directly calling the script - from any location.
This is a symlink resolver in Bash that works whether the link is a directory or a non-directory:
function readlinks {(
set -o errexit -o nounset
declare n=0 limit=1024 link="$1"
# If it's a directory, just skip all this.
if cd "$link" 2>/dev/null
then
pwd -P
return 0
fi
# Resolve until we are out of links (or recurse too deep).
while [[ -L $link ]] && [[ $n -lt $limit ]]
do
cd "$(dirname -- "$link")"
n=$((n + 1))
link="$(readlink -- "${link##*/}")"
done
cd "$(dirname -- "$link")"
if [[ $n -ge $limit ]]
then
echo "Recursion limit ($limit) exceeded." >&2
return 2
fi
printf '%s/%s\n' "$(pwd -P)" "${link##*/}"
)}
Note that all the cd and set stuff takes place in a subshell.
Try this:
cd $(dirname $([ -L $0 ] && readlink -f $0 || echo $0))
Since I've run into this many times over the years, and this time around I needed a pure bash portable version that I could use on OSX and linux, I went ahead and wrote one:
The living version lives here:
https://github.com/keen99/shell-functions/tree/master/resolve_path
but for the sake of SO, here's the current version (I feel it's well tested..but I'm open to feedback!)
Might not be difficult to make it work for plain bourne shell (sh), but I didn't try...I like $FUNCNAME too much. :)
#!/bin/bash
resolve_path() {
#I'm bash only, please!
# usage: resolve_path <a file or directory>
# follows symlinks and relative paths, returns a full real path
#
local owd="$PWD"
#echo "$FUNCNAME for $1" >&2
local opath="$1"
local npath=""
local obase=$(basename "$opath")
local odir=$(dirname "$opath")
if [[ -L "$opath" ]]
then
#it's a link.
#file or directory, we want to cd into it's dir
cd $odir
#then extract where the link points.
npath=$(readlink "$obase")
#have to -L BEFORE we -f, because -f includes -L :(
if [[ -L $npath ]]
then
#the link points to another symlink, so go follow that.
resolve_path "$npath"
#and finish out early, we're done.
return $?
#done
elif [[ -f $npath ]]
#the link points to a file.
then
#get the dir for the new file
nbase=$(basename $npath)
npath=$(dirname $npath)
cd "$npath"
ndir=$(pwd -P)
retval=0
#done
elif [[ -d $npath ]]
then
#the link points to a directory.
cd "$npath"
ndir=$(pwd -P)
retval=0
#done
else
echo "$FUNCNAME: ERROR: unknown condition inside link!!" >&2
echo "opath [[ $opath ]]" >&2
echo "npath [[ $npath ]]" >&2
return 1
fi
else
if ! [[ -e "$opath" ]]
then
echo "$FUNCNAME: $opath: No such file or directory" >&2
return 1
#and break early
elif [[ -d "$opath" ]]
then
cd "$opath"
ndir=$(pwd -P)
retval=0
#done
elif [[ -f "$opath" ]]
then
cd $odir
ndir=$(pwd -P)
nbase=$(basename "$opath")
retval=0
#done
else
echo "$FUNCNAME: ERROR: unknown condition outside link!!" >&2
echo "opath [[ $opath ]]" >&2
return 1
fi
fi
#now assemble our output
echo -n "$ndir"
if [[ "x${nbase:=}" != "x" ]]
then
echo "/$nbase"
else
echo
fi
#now return to where we were
cd "$owd"
return $retval
}
here's a classic example, thanks to brew:
%% ls -l `which mvn`
lrwxr-xr-x 1 draistrick 502 29 Dec 17 10:50 /usr/local/bin/mvn# -> ../Cellar/maven/3.2.3/bin/mvn
use this function and it will return the -real- path:
%% cat test.sh
#!/bin/bash
. resolve_path.inc
echo
echo "relative symlinked path:"
which mvn
echo
echo "and the real path:"
resolve_path `which mvn`
%% test.sh
relative symlinked path:
/usr/local/bin/mvn
and the real path:
/usr/local/Cellar/maven/3.2.3/libexec/bin/mvn
To work around the Mac incompatibility, I came up with
echo `php -r "echo realpath('foo');"`
Not great but cross OS
Here I present what I believe to be a cross-platform (Linux and macOS at least) solution to the answer that is working well for me currently.
crosspath()
{
local ref="$1"
if [ -x "$(which realpath)" ]; then
path="$(realpath "$ref")"
else
path="$(readlink -f "$ref" 2> /dev/null)"
if [ $? -gt 0 ]; then
if [ -x "$(which readlink)" ]; then
if [ ! -z "$(readlink "$ref")" ]; then
ref="$(readlink "$ref")"
fi
else
echo "realpath and readlink not available. The following may not be the final path." 1>&2
fi
if [ -d "$ref" ]; then
path="$(cd "$ref"; pwd -P)"
else
path="$(cd $(dirname "$ref"); pwd -P)/$(basename "$ref")"
fi
fi
fi
echo "$path"
}
Here is a macOS (only?) solution. Possibly better suited to the original question.
mac_realpath()
{
local ref="$1"
if [[ ! -z "$(readlink "$ref")" ]]; then
ref="$(readlink "$1")"
fi
if [[ -d "$ref" ]]; then
echo "$(cd "$ref"; pwd -P)"
else
echo "$(cd $(dirname "$ref"); pwd -P)/$(basename "$ref")"
fi
}
My answer here Bash: how to get real path of a symlink?
but in short very handy in scripts:
script_home=$( dirname $(realpath "$0") )
echo Original script home: $script_home
These are part of GNU coreutils, suitable for use in Linux systems.
To test everything, we put symlink into /home/test2/, amend some additional things and run/call it from root directory:
/$ /home/test2/symlink
/home/test
Original script home: /home/test
Where
Original script is: /home/test/realscript.sh
Called script is: /home/test2/symlink
My 2 cents. This function is POSIX compliant, and both the source and the destination can contain ->. However, I have not gotten it work with filenames that container newline or tabs, as ls in general has issues with those.
resolve_symlink() {
test -L "$1" && ls -l "$1" | awk -v SYMLINK="$1" '{ SL=(SYMLINK)" -> "; i=index($0, SL); s=substr($0, i+length(SL)); print s }'
}
I believe the solution here is the file command, with a custom magic file that only outputs the destination of the provided symlink.
This is the best solution, tested in Bash 3.2.57:
# Read a path (similar to `readlink`) recursively, until the physical path without any links (like `cd -P`) is found.
# Accepts any existing path, prints its physical path and exits `0`, exits `1` if some contained links don't exist.
# Motivation: `${BASH_SOURCE[0]}` often contains links; using it directly to extract your project's path may fail.
#
# Example: Safely `source` a file located relative to the current script
#
# source "$(dirname "$(rreadlink "${BASH_SOURCE[0]}")")/relative/script.sh"
#Inspiration: https://stackoverflow.com/a/51089005/6307827
rreadlink () {
declare p="$1" d l
while :; do
d="$(cd -P "$(dirname "$p")" && pwd)" || return $? #absolute path without symlinks
p="$d/$(basename "$p")"
if [ -h "$p" ]; then
l="$(readlink "$p")" || break
#A link must be resolved from its fully resolved parent dir.
d="$(cd "$d" && cd -P "$(dirname "$l")" && pwd)" || return $?
p="$d/$(basename "$l")"
else
break
fi
done
printf '%s\n' "$p"
}