pgrep multiple process names

Question

I want to get PIDs of two or more processes using "pgrep" command in Linux.

As we know pgrep syntax is

pgrep [options] <pattern>

Here is a hypothetical command which should return PIDs of two processes whose names are process1 and process2 respectively.

pgrep process1 OR process2 

What should be the pattern that needs to be used to achieve the above?

Gastongastralgia

what are the real process names you need to grep? – Few

The real process names are nginx and java – Gastongastralgia

From man pgrep: pgrep [options] pattern and pattern: Specifies an Extended Regular Expression for matching against the process names or command lines. – Countercheck

Answer 1

Try:

pgrep 'process1|process2'

Example:

 -->pgrep 'atd|cron'
1078
1093

 -->ps -eaf |grep -E 'atd|cron'
daemon    1078     1  0 Aug08 ?        00:00:00 /usr/sbin/atd -f
root      1093     1  0 Aug08 ?        00:00:19 /usr/sbin/cron -f
xxxx  14364  9597  0 11:56 pts/2    00:00:00 grep -E atd|cron

Dissimulation

Be careful, as this is totally wrong. Pgrep uses regexp matching, so atd|cron can match not only atd & cron but for instance rpc.statd or crond. – Marchetti

Its not wrong. Idea for this answer is to tell OP how to use Or condition. When pipe is used for OR condition, it was implied that regex is used. Yes, they need to use word boundaries to prevent false positive. – Dissimulation

You can just use exact match like this pgrep -x 'atd|cron', or pgrep '^(atd|cron)$'. – Liv