which

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which searches the folders in your $PATH, from left to right, and prints the first file with that name. It answers "where is this program on the disk?".

On RHEL, which for Bash users is an alias that also shows aliases and functions (alias which='(alias; declare -f) | /usr/bin/which --tty-only --read-alias --read-functions --show-tilde --show-dot').

To know which package a program comes from, use rpm -qf $(which NAME).

طريقة الكتابة

which [OPTIONS] PROGRAM [PROGRAM ...]

الخيارات 12

الأكثر استخدامًا

-a, --all: Print all matches in $PATH, not only the first one.
-i, --read-alias: Read aliases from standard input and report them too.
--skip-alias: Ignore --read-alias (use it to override the RHEL alias).
--read-functions: Read shell functions from standard input and report them too.
--skip-functions: Ignore --read-functions.
--skip-dot: Skip folders in $PATH that start with a dot.
--skip-tilde: Skip folders in $PATH that start with ~ and home folders.
--show-dot: If a $PATH folder starts with a dot, print ./PROGRAM.
--show-tilde: Print ~ instead of the full home folder path.
--tty-only: Stop reading options when the output is not a terminal (used by the RHEL alias).
-v, -V, --version: Show the version.
--help: Show help.

أمثلة 11

$ مستخدم عادي# بصلاحية root (أو مع sudo)

1Find where a program is
```
$which passwd
/usr/bin/passwd
```
The program file that runs when you type passwd.
2See all copies of a program in $PATH
```
$which -a python3
/usr/bin/python3
/usr/local/bin/python3
```
The first one wins. Two copies often explain "wrong version" problems.
3Find the package of a program
```
$rpm -qf $(which ss)
iproute-6.x.x.el10.x86_64
```
Now you know which package to update or reinstall.
4Check if a tool exists in a script
```
$which ansible >/dev/null 2>&1 && echo "ansible installed"
```
The exit code is 0 when found, 1 when not found.
5Show the alias too (RHEL default)
```
$which ll
alias ll='ls -l --color=auto'
	/usr/bin/ls
```
Because of the RHEL alias, which also shows aliases in an interactive shell.
6Use the plain program without the alias
```
$/usr/bin/which --skip-alias ll
```
In a script the alias does not exist; this shows what a script would find.
7Check the path of a privileged program in a review
```
$which -a sudo
```
Only /usr/bin/sudo should appear. Another sudo earlier in $PATH is a red flag.
8Find which shell a user would get
```
$which bash zsh fish
/usr/bin/bash
```
Only installed shells are printed; the others give an error message.
9Get the path for a cron job or a systemd unit
```
$which podman
/usr/bin/podman
```
cron and systemd use a short $PATH. Write the full path in ExecStart= and crontab lines.
10Check many tools at once before a deployment
```
$for t in git curl jq rsync; do which $t >/dev/null || echo "missing: $t"; done
```
Prints only the tools that are not installed.
11Compare with type
```
$which cd; type cd
```
which finds no file for cd (it is a built-in); type explains what it is.

انتبه

which only searches files in $PATH. It does not know built-ins like cd (use type).
sudo which NAME can give another answer, because root has a different $PATH.

نصائح للحفظ

which = where is the file? type = what will run? rpm -qf = which package?

`which`

ماذا يفعل

طريقة الكتابة

الخيارات 12

أمثلة 11

1Find where a program is

2See all copies of a program in $PATH

3Find the package of a program

4Check if a tool exists in a script

5Show the alias too (RHEL default)

6Use the plain program without the alias

7Check the path of a privileged program in a review

8Find which shell a user would get

9Get the path for a cron job or a systemd unit

10Check many tools at once before a deployment

11Compare with type

انتبه

نصائح للحفظ

الدليل الكامل

ماذا يفعل

طريقة الكتابة

الخيارات 12

أمثلة 11

1Find where a program is

2See all copies of a program in $PATH

3Find the package of a program

4Check if a tool exists in a script

5Show the alias too (RHEL default)

6Use the plain program without the alias

7Check the path of a privileged program in a review

8Find which shell a user would get

9Get the path for a cron job or a systemd unit

10Check many tools at once before a deployment

11Compare with type

انتبه

نصائح للحفظ

أوامر مرتبطة

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الدليل الكامل

`which`