How to read a sigmask of a process on Linux

Published: July 8th 2026 (week 28 of 2026) in linux

You can get the signal mask of a running process from the /proc filesystem, but how do you interpret it?

Get the sigmask of a running process

cat /proc/2137/status | grep -P '^Sig'

SigQ:	5/256411

SigPnd:	0000000000000000

SigBlk:	0000000000000000

SigIgn:	0000000000000000

SigCgt:	0000000028095207

The meaning of the each value is briefly explained by the proc_pid_status(5) man page. For example, the SigCgt field represents the "Mask (expressed in hexadecimal) indicating signals being caught". The proc_pid_status(5) man page then refers the reader to another one, namely signal(7).

The signal(7) man page has a section called Signal numbering for standard signals. This section contains a nice table that shows signals and their numbers on several processor architectures. The same information can also be obtained by running the following command:

Get number to signal mapping table

/usr/bin/kill -L

You can use this information to interpret the hexadecimal values you obtained by inspecting the /proc/<pid>/status file. Signal with number 1 sets the first bit, signal number 2 sets the second bit, and so on.

You can also act like a civilised person living in the 21st century, and not a bloody savage, and let the computer do the work for you:

/usr/bin/kill -l 0x0000000028095207

HUP

INT

QUIT

USR1

PIPE

TERM

CHLD

TSTP

WINCH

PWR

Just keep in mind that you must use the kill(1) command from the util-linux package, not the built-in of your shell. This is the reason why the examples used /usr/bin/kill ie, the full path to the executable, instead of just kill.

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