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.\" Copyright (c) 1995 Peter Wemm
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.Dd November 28, 2022
.Dt SETPROCTITLE 3
.Os
.Sh NAME
.Nm setproctitle
.Nm setproctitle_fast
.Nd set process title
.Sh SYNOPSIS
.In unistd.h
.Ft void
.Fn setproctitle "const char *fmt" "..."
.Ft void
.Fn setproctitle_fast "const char *fmt" "..."
.Sh DESCRIPTION
The
.Fn setproctitle
library routine sets the process title that appears on the
.Xr ps 1
command.
The
.Fn setproctitle_fast
variant is optimized for high frequency updates, but may make the
.Xr ps 1
command slightly slower by not updating the kernel cache of the program
arguments.
.Pp
The title is set from the executable's name, followed by the
result of a
.Xr printf 3
style expansion of the arguments as specified by the
.Va fmt
argument.
If the
.Va fmt
argument begins with a
.Dq -
character, the executable's name is skipped.
.Pp
If
.Va fmt
is NULL, the process title is restored.
.Sh EXAMPLES
To set the title on a daemon to indicate its activity:
.Bd -literal -offset indent
setproctitle("talking to %s", inet_ntoa(addr));
.Ed
.Sh SEE ALSO
.Xr ps 1 ,
.Xr w 1 ,
.Xr kvm 3 ,
.Xr kvm_getargv 3 ,
.Xr printf 3 ,
.Xr setprogname 3
.Sh STANDARDS
The
.Fn setproctitle
function
is implicitly non-standard.
Other methods of causing the
.Xr 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
.Fn setproctitle
if present.
.Pp
Unfortunately, it is possible that there are other calling conventions
to other versions of
.Fn setproctitle ,
although none have been found by the author as yet.
This is believed to be
the predominant convention.
.Pp
It is thought that the implementation is compatible with other systems,
including
.Nx
and
.Bsx .
.Sh HISTORY
The
.Fn setproctitle
function
first appeared in
.Fx 2.2 .
The
.Fn setproctitle_fast
function first appeared in
.Fx 12 .
Other operating systems have
similar functions.
.Sh AUTHORS
.An -nosplit
.An Peter Wemm Aq Mt peter@FreeBSD.org
stole the idea from the
.Sy "Sendmail 8.7.3"
source code by
.An Eric Allman Aq Mt eric@sendmail.org .
.Sh BUGS
Never pass a string with user-supplied data as a format without using
.Ql %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
.Fn snprintf ,
as the resulting string may still contain user-supplied conversion specifiers
for later interpolation by
.Fn setproctitle .
.Pp
Always use the proper secure idiom:
.Pp
.Dl setproctitle("%s", string);