Introduction
Before we start discussing pgrep command in linux, let's first understand-What is a Pgrep Command ?
The pgrep
command in Linux is used to search for processes based on their criteria and return their process IDs (PIDs). It provides a quick and efficient way to identify running processes by specifying attributes such as the process name, user, group, command line, or other criteria. The pgrep
command is a useful tool for process management and troubleshooting in Linux systems.
In this tutorial, we have covered the basics of the Linux pgrep
.
How to Use the pgrep
Command
The pgrep
command has the following syntax:
pgrep [OPTIONS] <PATTERN>
Extended regular expressions are used to specify the matching <PATTERN>
.
pgrep
displays the PIDs of all running programs that match the given name when run without any options. To find the PID of the SSH server, for example, type:
pgrep ssh
The PIDs of all running processes with names that match "ssh" will be displayed on the screen. The output is empty if no matches are found.
Output
1039
2257
6850
31279
When at least one running process has the same name as the one requested, the command returns 0
. Otherwise, 1
is the exit code. When building shell scripts, this can come in handy.
Use pkill
to deliver signals to the corresponding processes. This command is a wrapper for pkill
, and it uses the same arguments and pattern matching as that command.
Each matched process ID is printed on a new line by pgrep
. You can use the -d
option to specify a different delimiter. If you want to use a space as a delimiter, for example, type:
pgrep ssh -d' '
Output
1039 2257 6850 31279
The -l
option instructs pgrep
to display the process's name as well as its ID:
pgrep ssh -l
pgrep
does the search using regular expressions and returns a list of all processes with the word "ssh" in their names:
Output
1039 sshd
2257 ssh-agent
6850 ssh
31279 ssh-agent
If you only want to match processes whose names match the search pattern exactly, you'd use:
pgrep '^ssh$' -l
Output
6850 ssh
Pgrep
matches just against the process name by default. The command matches against the entire argument list when the -f
option is provided.
pgrep -f ssh
To tell pgrep
to display processes run by a certain user, use the -u
option:
pgrep -u root
To specify several users, use commas to separate their names:
pgrep -u root,mark
You can also mix and match search patterns and options. To print all processes and their names that run under user "mark" and have the word "gnome" in their names, type:
pgrep -l -u mark gnome
Use the -n
(for newest) or -o
(for oldest) options to display only the processes that were started the least recently (oldest) or the most recently (newest).
To identify the most recent process initiated by the user "mark," for example, type:
pgrep -lnu mark
You can also combine the selections without a space between them and with a single dash, as seen in the example above.
Use the -v
option to reverse the matching, displaying only processes that do not meet the supplied criteria. All processes that are not being executed by user "mark" will be printed using the following command:
pgrep -v -u mark
The -c
option instructs pgrep
to just print the number of matching processes. To find the processes that run as user "mark," for example, type:
pgrep -c -u mark
FAQs on Pgrep Command in Linux
How does the pgrep
command work?
The pgrep
command searches for processes that match a specific criterion specified as an argument. It scans the process table and outputs the PIDs of matching processes.
What are the common criteria used with the pgrep
command?
You can use various criteria with the pgrep
command, such as the process name (-x
option), user/group (-u
and -g
options), parent process ID (-P
option), command line (-f
option), and more.
How do I use the pgrep
command to search for processes by name?
To search for processes by name using pgrep
, simply provide the process name as an argument. For example, pgrep sshd
will retrieve the PIDs of all processes with the name "sshd".
Can I use pgrep
to search for processes by their command line arguments?
Yes, you can use the -f
option with pgrep
to search for processes based on their command line arguments. For example, pgrep -f "nginx -c /etc/nginx.conf"
will find processes with the specified command line.
How can I search for processes owned by a specific user with pgrep
?
Use the -u
option followed by the username to search for processes owned by a specific user. For example, pgrep -u username
will retrieve the PIDs of processes owned by "username".
Is it possible to negate criteria in pgrep
?
Yes, you can use the -v
option to invert the matching criteria. For example, pgrep -v sshd
will return PIDs of all processes except those with the name "sshd".
How does the pgrep
command differ from pidof
?
While both pgrep
and pidof
retrieve process IDs, pgrep
offers more flexibility in searching for processes based on various criteria. pidof
primarily searches for processes by their executable names and returns a single PID.
Conclusion
The pgrep
command is used to determine the PIDs of a running application using various criteria.
Visit the pgrep man
page or type man pgrep
in your terminal for more information about the pgrep
command.
If you have any queries, please leave a comment below and we’ll be happy to respond to them.