Print all PID folders from /proc line-by-line with this format (( PID: command-line ))

courteous · 12-12-2010, 09:25 AM

How do you extract all numeric folders from PIDs variable, which is defined as:

Code:

PIDs="$(ls -v /proc/)"  # -v for numeric sort

I would like to print all PID (ie. numeric) folders from /proc folder. This does not work:

Code:

numberOfPIDs="$(ls /proc/ | wc -l)"

for ((x=0; x < $numberOfPIDs; x++)); do
	echo "$PIDsource | cut -d' ' -f$x"
done

colucix · 12-12-2010, 09:36 AM

Code:

ls -dv [1-9]*

lists all the PID directories under /proc numerically sorted.

courteous · 12-12-2010, 02:26 PM

Excellent.
How can I use your snippet outside /proc folder? Why this doesn't work:

Code:

ls -dv [1-9]* /proc/

impert · 12-12-2010, 03:01 PM

Code:

ls -dv /proc/[1-9]*

courteous · 12-12-2010, 03:09 PM

This for loop is much better, but it still gives plenty of errors:

Code:

PIDlist="$(ls -dv /proc/[1-9]* | cut -d '/' -f3)" # I need only PIDs
PIDnumber="$(ls /proc/ | wc -l)"

for i in "$PIDlist"; do
	printf "%4u | %10s\n" "$i" "$(cat /proc/$i/cmdline)"
done

Error example: cat: 4: No such file or directory. Indeed, in terminal cat /proc/4/cmdline returns nothing.

colucix · 12-12-2010, 04:27 PM

Keep it simple. You might loop over the /proc/PID directories and use parameter substitution or the basename command to retrieve PID. Example:

Code:

for i in /proc/[1-9]*
do
  command="$(cat $i/cmdline)"
  command=${command:-<not available>}         # if command is not set or empty use default
  printf "%5d | %s\n" ${i##*/} "$command"     # ${i##*/} is the same as $(basename $i)
done | sort -k1n

Hope this helps.

courteous · 12-12-2010, 04:36 PM

What do hash-hash-star-slash, that is ${i##*/}, in printf do?

EDIT: Oh, I'm sorry, now I see it in comment. Forward to man basename!

Thank you again.

colucix · 12-12-2010, 04:47 PM

Actually it is substring removal. Look at the advanced bash scripting guide, here.

Code:

${string##substring}

    Deletes longest match of $substring from front of $string.

In this case it deletes the longest match of any string * followed by a slash, acting as the basename command.