<utmp.h> has been deprecated since 2001 in favour of <utmpx.h>.
On glibc systems, utmp is just an alias to utmpx, so there is no
functional change using one over the other.
However, on the musl libc, a library (utmps) can be used to provide
utmpx functionality - but not utmp. This means that procps either
doesn't work properly (`w` shows nothing under musl with default no-op
implementation), or fails to build (utmps provides utmpx.h but no
utmp.h).
This commit will use utmpx.h where available, which allows `w` to work
correctly with utmps and has no change on glibc systems.
Often pidof is used in shell scripts in this form:
if pidof daemon >/dev/null; then
...
fi
The redirection to /dev/null is needed because otherwise the script
would output the found PIDs.
Let's add a -q option which, similary to grep, just sets the exit code.
Also exit on first match, as there is no reason to proceed further when
at least a process is matched.
Tested with:
$ ./pidof bash
17701 14019 5276 2967
$ echo $?
0
$ ./pidof bashx
$ echo $?
1
$ ./pidof -q bash
$ echo $?
0
$ ./pidof -q bashx
$ echo $?
1
See https://en.wikipedia.org/wiki/ANSI_escape_code#8-bit
Support standard and high intensity colors. The default
ncurses colors ARE the high intensity colors - represented
via an 8 bit ansi escape sequence here.
See https://en.wikipedia.org/wiki/ANSI_escape_code#8-bit
Support standard and high intensity colors. The default
ncurses colors ARE the high intensity colors - represented
via an 8 bit ansi escape sequence here.
We read /proc/stat using a statically sized buffer. This was increased
to 64kB in 2005 via commit 777fcd3cf1 "/proc/stat for 1024 CPUs".
Unfortunately in 2020, 1024 CPUs is not enough for anyone. I have a
large machine where /proc/stat is 74kB, and vmstat gives incorrect
output.
Double the buffer to 128kB in the confidence that 2048 CPUs is actually
enough for anyone.
Signed-off-by: Anton Blanchard <anton@ozlabs.org>
New command, pwait! Waits for another process to finish just like
pgrep finds or pkill kills another process.
References:
procps-ng/procps!97
Signed-off-by: Craig Small <csmall@dropbear.xyz>
With glibc, each time the strftime() function is used (twice per process
in a typical ps -fe run), a stat("/etc/localtime") system call is used
to determine the timezone. Not only does this add extra system call
overhead, but when multiple ps processes are trying to access this
file (or multiple glibc programs using strftime) in parallel, this can
trigger significant lock contention within the OS kernel.
Since ps is not intended to run for long periods of time as a
daemon (during which the system timezone could be altered and PS might
reasonably be expected to adapt its output), there is no benefit to
repeatedly doing this stat(). To stop this behavior, explicitly set the
TZ variable to its default value (:/etc/localtime) whenever it is unset.
glibc will then cache the stat() result.
With glibc, each time the strftime() function is used (twice per process
in a typical ps -fe run), a stat("/etc/localtime") system call is used
to determine the timezone. Not only does this add extra system call
overhead, but when multiple ps processes are trying to access this
file (or multiple glibc programs using strftime) in parallel, this can
trigger significant lock contention within the OS kernel.
Since ps is not intended to run for long periods of time as a
daemon (during which the system timezone could be altered and PS might
reasonably be expected to adapt its output), there is no benefit to
repeatedly doing this stat(). To stop this behavior, explicitly set the
TZ variable to its default value (:/etc/localtime) whenever it is unset.
glibc will then cache the stat() result.
