CODEWITHSUNDEEP
bashshellunix
user1508682
user1508682

Reputation: 1371

In unix how to find out if process running and return true/false?

I'm writing a unix shell script and need to check if there are currently running processes with "xyz" in their directory. If yes than continue to next command and show text like "Found It".

If not than don't continue and display text like "Process Not Found".

I tried something like this:

if ps -ef | grep xyz
then
    echo "XYZ Process Found!"
else
    echo "XYZ Process Not Found!"
fi

But it just showing me the processes and display "process found" even if there's no xyz process.

Upvotes: 1

Views: 7653

Answers (4)

progonkpa
progonkpa

Reputation: 3950

is_xyz_running() {
  [ "$(pgrep xyz)" ] && echo true || echo false
}

Upvotes: 0

Elliott Frisch
Elliott Frisch

Reputation: 201537

I believe you want to check the output of the command against a value using Command substition, from the linked bash-hackers wiki The command substitution expands to the output of commands. These commands are executed in a subshell, and their stdout data is what the substitution syntax expands to. Also, count the lines and remove grep. Something like,

if [[ $(ps -ef | grep xyz | grep -v grep | wc -l) != 0 ]]; then
        echo "XYZ Process Found!"
else
        echo "XYZ Process Not Found!"
fi

Edit

Based on the comments below, you should probably use

if [[ $(ps -ef | grep -c xyz)  -ne 1 ]]; then

which is a lot easier to read.

Upvotes: 5

anishsane
anishsane

Reputation: 20980

When you run grep xyz, that process - grep xyz - is also running & thus shown in the output of ps -ef.
This running process command line contains xyz. Thus grep passes that line to output.
Hence you always get zero exit status - i.e. success.

2 Solutions:

  1. use if ps -ef | grep '[x]yz'; then. (You may want to suppress grep output with -q)
    The grep command being run is grep [x]yz. This gets printed in ps -ef output.
    Obviously, grep filters out this line. [x]yz could be matched with \[x\]yz, not with [x]yz.

  2. use if pgrep -f xyz >/dev/null; then
    Check man pgrep for more details..

Upvotes: 3

Martin Tournoij
Martin Tournoij

Reputation: 27852

You can also use pgrep. From pgrep(1):

pgrep looks through the currently running processes and lists the process IDs which match the selection criteria to stdout.

[...]

EXIT STATUS
0 One or more processes matched the criteria.
1 No processes matched.
2 Syntax error in the command line.
3 Fatal error: out of memory etc.

Example output:

[~]% pgrep xterm
18231
19070
31727

You can use it in an if statement like so:

if pgrep xterm > /dev/null; then
  echo Found xterm
else
  echo xterm not found
fi

Note: pgrep is not a standard utility (ie. it's not in POSIX), but widely available on at least Linux and I believe most BSD systems.

Upvotes: 2

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