setproctitle_fast(3)

setproctitle_fast3

Set process title

Part of setproctitle(3).

Usage

#include <unistd.h>

void

setproctitle(const char *fmt, ...);

void

setproctitle_fast(const char *fmt, ...);

Overview

The setproctitle() library routine sets the process title that appears on the ps(1) command. The setproctitle_fast() variant is optimized for high frequency updates, but may make the ps(1) command slightly slower by not updating the kernel cache of the program arguments.

The title is set from the executable's name, followed by the result of a printf(3) style expansion of the arguments as specified by the fmt argument. If the fmt argument begins with a “-” character, the executable's name is skipped.

If fmt is NULL, the process title is restored.

Examples

To set the title on a daemon to indicate its activity:

setproctitle("talking to %s", inet_ntoa(addr));

Releases

21 releases since FreeBSD 11.3-RELEASE; the text changed 10 times.

  1. 11.3
  2. 11.4
  3. 12.1
  4. 12.2
  5. 12.3
  6. 12.4
  7. 13.0–13.1
  8. 13.2
  9. 13.3–13.5
  10. 14.0–14.2
  11. 14.3–16.0

Standards

The setproctitle() function is implicitly non-standard. Other methods of causing the ps(1) command line to change, including copying over the argv[0] string are also implicitly non-portable. It is preferable to use an operating system supplied setproctitle() if present.

Unfortunately, it is possible that there are other calling conventions to other versions of setproctitle(), although none have been found by the author as yet. This is believed to be the predominant convention.

It is thought that the implementation is compatible with other systems, including NetBSD and BSD/OS.

History

The setproctitle() function first appeared in FreeBSD 2.2. The setproctitle_fast() function first appeared in FreeBSD 12. Other operating systems have similar functions.

Authors

Peter Wemm ⟨[email protected]⟩ stole the idea from the Sendmail 8.7.3 source code by Eric Allman ⟨[email protected]⟩.

Bugs

Never pass a string with user-supplied data as a format without using ‘%s’. An attacker can put format specifiers in the string to mangle your stack, leading to a possible security hole. This holds true even if the string was built using a function like snprintf(), as the resulting string may still contain user-supplied conversion specifiers for later interpolation by setproctitle().

Always use the proper secure idiom:

setproctitle("%s", string);

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.