How to get $HOME directory when switching to a different user in bash?
BashBash Problem Overview
I need to execute part of a bash script as a different user, and inside that user's $HOME
directory. However, I'm not sure how to determine this variable. Switching to that user and calling $HOME
does not provide the correct location:
# running script as root, but switching to a different user...
su - $different_user
echo $HOME
# returns /root/ but should be /home/myuser
Update:
It appears that the issue is with the way that I am trying to switch users in my script:
$different_user=deploy
# create user
useradd -m -s /bin/bash $different_user
echo "Current user: `whoami`"
# Current user: root
echo "Switching user to $different_user"
# Switching user to deploy
su - $different_user
echo "Current user: `whoami`"
# Current user: root
echo "Current user: `id`"
# Current user: uid=0(root) gid=0(root) groups=0(root)
sudo su $different_user
# Current user: root
# Current user: uid=0(root) gid=0(root) groups=0(root)
What is the correct way to switch users and execute commands as a different user in a bash script?
Bash Solutions
Solution 1 - Bash
Update: Based on this question's title, people seem to come here just looking for a way to find a different user's home directory, without the need to impersonate that user.
In that case, the simplest solution is to use tilde expansion with the username of interest, combined with eval
(which is needed, because the username must be given as an unquoted literal in order for tilde expansion to work):
eval echo "~$different_user" # prints $different_user's home dir.
Note: The usual caveats regarding the use of eval
apply; in this case, the assumption is that you control the value of $different_user
and know it to be a mere username.
By contrast, the remainder of this answer deals with impersonating a user and performing operations in that user's home directory.
Note:
- Administrators by default and other users if authorized via the
sudoers
file can impersonate other users viasudo
. - The following is based on the default configuration of
sudo
- changing its configuration can make it behave differently - seeman sudoers
.
The basic form of executing a command as another user is:
sudo -H -u someUser someExe [arg1 ...]
# Example:
sudo -H -u root env # print the root user's environment
Note:
- If you neglect to specify
-H
, the impersonating process (the process invoked in the context of the specified user) will report the original user's home directory in$HOME
. - The impersonating process will have the same working directory as the invoking process.
- The impersonating process performs no shell expansions on string literals passed as arguments, since no shell is involved in the impersonating process (unless
someExe
happens to be a shell) - expansions by the invoking shell - prior to passing to the impersonating process - can obviously still occur.
Optionally, you can have an impersonating process run as or via a(n impersonating) shell, by prefixing someExe
either with -i
or -s
- not specifying someExe ...
creates an interactive shell:
-
-i
creates a login shell forsomeUser
, which implies the following:someUser
's user-specific shell profile, if defined, is loaded.$HOME
points tosomeUser
's home directory, so there's no need for-H
(though you may still specify it)- The working directory for the impersonating shell is the
someUser
's home directory.
-
-s
creates a non-login shell:- no shell profile is loaded (though initialization files for interactive nonlogin shells are; e.g.,
~/.bashrc
) - Unless you also specify
-H
, the impersonating process will report the original user's home directory in$HOME
. - The impersonating shell will have the same working directory as the invoking process.
- no shell profile is loaded (though initialization files for interactive nonlogin shells are; e.g.,
Using a shell means that string arguments passed on the command line MAY be subject to shell expansions - see platform-specific differences below - by the impersonating shell (possibly after initial expansion by the invoking shell); compare the following two commands (which use single quotes to prevent premature expansion by the invoking shell):
# Run root's shell profile, change to root's home dir.
sudo -u root -i eval 'echo $SHELL - $USER - $HOME - $PWD'
# Don't run root's shell profile, use current working dir.
# Note the required -H to define $HOME as root`s home dir.
sudo -u root -H -s eval 'echo $SHELL - $USER - $HOME - $PWD'
What shell is invoked is determined by "the SHELL environment variable if it is set or the shell as specified in passwd(5)" (according to man sudo
). Note that with -s
it is the invoking user's environment that matters, whereas with -i
it is the impersonated user's.
Note that there are platform differences regarding shell-related behavior (with -i
or -s
):
-
sudo
on Linux apparently only accepts an executable or builtin name as the first argument following-s
/-i
, whereas OSX allows passing an entire shell command line; e.g., OSX acceptssudo -u root -s 'echo $SHELL - $USER - $HOME - $PWD'
directly (no need foreval
), whereas Linux doesn't (as ofsudo 1.8.95p
). -
Older versions of
sudo
on Linux do NOT apply shell expansions to arguments passed to a shell; for instance, withsudo 1.8.3p1
(e.g., Ubuntu 12.04),sudo -u root -H -s echo '$HOME'
simply echoes the string literal "$HOME" instead of expanding the variable reference in the context of the root user. As of at leastsudo 1.8.9p5
(e.g., Ubuntu 14.04) this has been fixed. Therefore, to ensure expansion on Linux even with oldersudo
versions, pass the the entire command as a single argument toeval
; e.g.:sudo -u root -H -s eval 'echo $HOME'
. (Although not necessary on OSX, this will work there, too.) -
The
root
user's$SHELL
variable contains/bin/sh
on OSX 10.9, whereas it is/bin/bash
on Ubuntu 12.04.
Whether the impersonating process involves a shell or not, its environment will have the following variables set, reflecting the invoking user and command: SUDO_COMMAND
, SUDO_USER
, SUDO_UID=
, SUDO_GID
.
See man sudo
and man sudoers
for many more subtleties.
Tip of the hat to @DavidW and @Andrew for inspiration.
Solution 2 - Bash
In BASH, you can find a user's $HOME
directory by prefixing the user's login ID with a tilde character. For example:
$ echo ~bob
This will echo out user bob
's $HOME
directory.
However, you say you want to be able to execute a script as a particular user. To do that, you need to setup sudo. This command allows you to execute particular commands as either a particular user. For example, to execute foo
as user bob
:
$ sudo -i -ubob -sfoo
This will start up a new shell, and the -i
will simulate a login with the user's default environment and shell (which means the foo
command will execute from the bob's
$HOME` directory.)
Sudo is a bit complex to setup, and you need to be a superuser just to be able to see the shudders file (usually /etc/sudoers
). However, this file usually has several examples you can use.
In this file, you can specify the commands you specify who can run a command, as which user, and whether or not that user has to enter their password before executing that command. This is normally the default (because it proves that this is the user and not someone who came by while the user was getting a Coke.) However, when you run a shell script, you usually want to disable this feature.
Solution 3 - Bash
For the sake of an alternative answer for those searching for a lightweight way to just find a user's home dir...
Rather than messing with su
hacks, or bothering with the overhead of launching another bash
shell just to find the $HOME
environment variable...
Lightweight Simple Homedir Query via Bash
There is a command specifically for this: getent
getent passwd someuser | cut -f6 -d:
getent
can do a lot more... just see the man page. The passwd
nsswitch database will return the user's entry in /etc/passwd
format. Just split it on the colon :
to parse out the fields.
It should be installed on most Linux systems (or any system that uses GNU Lib C (RHEL: glibc-common
, Deb: libc-bin
)
Solution 4 - Bash
You want the -u
option for sudo
in this case. From the man
page:
The -u (user) option causes sudo to run the specified command as a user other than root.
If you don't need to actually run it as them, you could move to their home directory with ~<user>
. As in, to move into my home directory you would use cd ~chooban
.
Solution 5 - Bash
So you want to:
- execute part of a bash script as a different user
- change to that user's $HOME directory
Inspired by this answer, here's the adapted version of your script:
#!/usr/bin/env bash
different_user=deploy
useradd -m -s /bin/bash "$different_user"
echo "Current user: $(whoami)"
echo "Current directory: $(pwd)"
echo
echo "Switching user to $different_user"
sudo -u "$different_user" -i /bin/bash - <<-'EOF'
echo "Current user: $(id)"
echo "Current directory: $(pwd)"
EOF
echo
echo "Switched back to $(whoami)"
different_user_home="$(eval echo ~"$different_user")"
echo "$different_user home directory: $different_user_home"
When you run it, you should get the following:
Current user: root
Current directory: /root
Switching user to deploy
Current user: uid=1003(deploy) gid=1003(deploy) groups=1003(deploy)
Current directory: /home/deploy
Switched back to root
deploy home directory: /home/deploy
Solution 6 - Bash
This works in Linux. Not sure how it behaves in other *nixes.
getent passwd "${OTHER_USER}"|cut -d\: -f 6
Solution 7 - Bash
The title of this question is How to get $HOME directory of different user in bash script? and that is what people are coming here from Google to find out.
There is a safe way to do this!
on Linux/BSD/macOS/OSX without sudo or root
user=pi
user_home=$(bash -c "cd ~$(printf %q $USER) && pwd")
NOTE: The reason this is safe is because bash (even versions prior to 4.4) has its own printf
function that includes:
> %q quote the argument in a way that can be reused as shell input
See: help printf
Compare the how other answers here respond to code injection
# "ls /" is not dangerous so you can try this on your machine
# But, it could just as easily be "sudo rm -rf /*"
$ user="root; ls /"
$ printf "%q" "$user"
root\;\ ls\ /
# This is what you get when you are PROTECTED from code injection
$ user_home=$(bash -c "cd ~$(printf "%q" "$user") && pwd"); echo $user_home
bash: line 0: cd: ~root; ls /: No such file or directory
# This is what you get when you ARE NOT PROTECTED from code injection
$ user_home=$(bash -c "cd ~$user && pwd"); echo $user_home
bin boot dev etc home lib lib64 media mnt ono opt proc root run sbin srv sys tmp usr var /root
$ user_home=$(eval "echo ~$user"); echo $user_home
/root bin boot dev etc home lib lib64 media mnt ono opt proc root run sbin srv sys tmp usr var
on Linux/BSD/macOS/OSX as root
If you are doing this because you are running something as root
then you can use the power of sudo:
user=pi
user_home=$(sudo -u $user sh -c 'echo $HOME')
on Linux/BSD (but not modern macOS/OSX) without sudo or root
If not, the you can get it from /etc/passwd
. There are already lots of examples of using eval
and getent
, so I'll give another option:
user=pi
user_home=$(awk -v u="$user" -v FS=':' '$1==u {print $6}' /etc/passwd)
I would really only use that one if I had a bash script with lots of other awk oneliners and no uses of cut
. While many people like to "code golf" to use the fewest characters to accomplish a task, I favor "tool golf" because using fewer tools gives your script a smaller "compatibility footprint". Also, it's less man pages for your coworker or future-self to have to read to make sense of it.
Solution 8 - Bash
I was also looking for this, but didn't want to impersonate a user to simply acquire a path!
user_path=$(grep $username /etc/passwd|cut -f6 -d":");
Now in your script, you can refer to $user_path
in most cases would be /home/username
Assumes: You have previously set $username
with the value of the intended users username.
Source: http://www.unix.com/shell-programming-and-scripting/171782-cut-fields-etc-passwd-file-into-variables.html
Solution 9 - Bash
Quick and dirty, and store it in a variable:
USER=somebody
USER_HOME="$(echo -n $(bash -c "cd ~${USER} && pwd"))"
Solution 10 - Bash
I was struggling with this question because I was looking for a way to do this in a bash script for OS X, hence /etc/passwd was out of the question, and my script was meant to be executed as root, therefore making the solutions invoking eval or bash -c dangerous as they allowed code injection into the variable specifying the username.
Here is what I found. It's simple and doesn't put a variable inside a subshell. However it does require the script to be ran by root as it sudos into the specified user account.
Presuming that $SOMEUSER contains a valid username:
echo "$(sudo -H -u "$SOMEUSER" -s -- "cd ~ && pwd")"
I hope this helps somebody!
Solution 11 - Bash
If the user doesn't exist, getent
will return an error.
Here's a small shell function that doesn't ignore the exit code of getent
:
get_home() {
local result; result="$(getent passwd "$1")" || return
echo $result | cut -d : -f 6
}
Here's a usage example:
da_home="$(get_home missing_user)" || {
echo 'User does NOT exist!'; exit 1
}
# Now do something with $da_home
echo "Home directory is: '$da_home'"
Solution 12 - Bash
The output of getent passwd username
can be parsed with a Bash regular expression
OTHER_HOME="$(
[[ "$(
getent \
passwd \
"${OTHER_USER}"
)" =~ ([^:]*:){5}([^:]+) ]] \
&& echo "${BASH_REMATCH[2]}"
)"
Solution 13 - Bash
If you have sudo active, just do:
sudo su - admin -c "echo \$HOME"
> NOTE: replace admin
for the user you want to get the home directory