ps outputs a newline after every entry. What are you trying to accomplish?
Do you have a username that contains a newline character? If so… why?!
this post was submitted on 02 Oct 2024
26 points (100.0% liked)
Linux
48287 readers
651 users here now
From Wikipedia, the free encyclopedia
Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
Rules
- Posts must be relevant to operating systems running the Linux kernel. GNU/Linux or otherwise.
- No misinformation
- No NSFW content
- No hate speech, bigotry, etc
Related Communities
Community icon by Alpár-Etele Méder, licensed under CC BY 3.0
founded 5 years ago
MODERATORS
Security by overcomplication
Kinda hard to encode it in /etc/passwd, which separates entries with newlines and fields of an entry with colons.
Of course, you can activate some alternative user database in /etc/nsswitch.conf and then you can have your usernames with newlines in them, but at least half of the tools on your system that process usernames will take that personally…
If I do ps aux | grep root, then the newline is preserved. So I'm not sure what exactly the problem is. There is a user option for ps, but it does not work with aux, ps --user root . You can ps ax --user root, but I'm not sure if this output is what you want.
Btw if you grep, then I recommend using ^user , so it only matches the beginning of each line (the actual username), as ps aux | \grep ^root (notice the backslash). Do you have an alias for grep? Try \grep instead. The backslash in front of the command will use the actual command and ignore your alias.
Here is a little bonus to have in mind: You can convert newline characters to null, then grep with option null, and at last convert null characters back to newline. Now I don't think its useful in this case, but its good to know; therefore its a bonus information:
ps aux | tr '\n' '\0' | \grep --null-data ^root | tr '\0' '\n'
tbh you should prolly use pgrep instead of piping ps into grep
what do you mean the output doesnt keep the LF? what LF?
ps also has -u and -U switches to filter by users
I'm not really sure what it is you're asking for here. As another commenter said, ps outputs a list of newline separated entries (using \n, the standard LF character). I even ran some sanity checks to make sure it wasn't using \r\n (CR LF) with the following:
$ ps aux | grep $USER | tr -cd "\n" | wc -m
14
$ ps aux | grep $USER | tr -cd "\r" | wc -m
0
The output of ps aux | grep $USER is consistent with the formatting of ps aux. I also found that ps aux | grep $USER was consistent with ps -fp $(pgrep -d, -u $USER) except that ps -fp $(pgrep -d, -u $USER) shows the header (UID PID PPID C STIME TTY TIME CMD), does not show the processes related to the command (entries of ps aux and grep --color=auto $USER), and does not show grep's keyword matching by highlighting all matches within a line. It is otherwise completely identical.
Can you provide the output that you are getting that is unsatisfactory to you? I don't think I can otherwise understand where the issue is.