On 9/18/25 4:45 AM, Alexis wrote: > However, the command line i provided in my post was: > > # ps ax | grep X > > where the `grep` is GNU grep, and will match _any_ instance of the > character 'X' in the process list, not just a process that's literally > nothing more than 'X'. That's why it listed Xwayland and the grep > process itself in the output: > > 3576 tty1 Sl+ 0:00 Xwayland :0 -rootless -core -terminate - > listenfd 26 -listenfd 27 -displayfd 67 -wm 64 > 12043 pts/21 S+ 0:00 grep --color=auto X > > It would have also listed Xnest, had it been running. > > That's how Basic Regular Expressions (BREs), as used by default by GNU > grep, work. If one wanted to match a literal 'X' and nothing more, one > would use the -F option to GNU grep, or fgrep, to indicate that one > doesn't want the pattern to be interpreted as an RE, but as a fixed string.
Well, no. $ ps ax | grep -F bas [...] 753347 pts/6 Ss+ 0:00 /bin/bash 1269600 pts/7 Ss 0:01 /bin/bash 1770581 pts/4 Ss 0:09 /bin/bash 1992403 pts/8 Ss 0:01 /bin/bash [...] Fixed strings != "nothing more", ironically you tend to need regex for word anchors like \b $ ps ax | grep '\bbas\b' $ ps ax | grep '\bbash\b' [...] 1269600 pts/7 Ss 0:01 /bin/bash 1770581 pts/4 Ss 0:09 /bin/bash 1992403 pts/8 Ss 0:01 /bin/bash 2226387 pts/9 Ss+ 0:25 /bin/bash [...] Personally I recommend $ pgrep -af '\bbash\b' 1393 -bash 1788 /bin/bash 1962 -bash 559140 bash 753347 /bin/bash 1269600 /bin/bash 1770581 /bin/bash 1992403 /bin/bash [...] pgrep won't catch the pipe to grep :) it also has -f, whose lack allows matching only inside the invoking exe name. -- Eli Schwartz
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