142 lines
4.6 KiB
Groff
142 lines
4.6 KiB
Groff
.\" (C) Copyright 2020 Craig Small <csmall@dropbear.xyz>
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.\"
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.\" %%%LICENSE_START(LGPL_2.1+)
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.\" This manual is free software; you can redistribute it and/or
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.\" modify it under the terms of the GNU Lesser General Public
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.\" License as published by the Free Software Foundation; either
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.\" version 2.1 of the License, or (at your option) any later version.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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.\" Lesser General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU Lesser General Public
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.\" License along with this library; if not, write to the Free Software
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.\" Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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.\" %%%LICENSE_END
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.\"
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.TH PROCPS_MISC 3 2020-10-20 "libproc-2"
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.\" Please adjust this date whenever revising the manpage.
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.\"
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.SH NAME
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procps_misc \- API to system information in the /proc filesystem
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.SH SYNOPSIS
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.nf
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.B #include <proc/sysinfo.h>
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.PP
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.B long procps_cpu_count(void);
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.B long procps_hertz_get(void);
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.BI "int procps_loadavg(double * " av1 ", double * " av5 ", double * " av15 ");"
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.B unsigned int procps_pid_length(void);
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.PP
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.B #include <proc/version.h>
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.PP
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.B int procps_linux_version(void);
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.sp
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Link with \fI\-lprocps\fP.
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.SH DESCRIPTION
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This manual page describes the miscellaneous API functions of the
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.B procps
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library.
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.BR procps_cpu_count ()
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returns the number of CPUs that are currently online. On most systems returns
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the value of
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.BI sysconf( _SC_NPROCESSORS_ONLN )
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or assumed to be \fI1\fR.
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.BR procps_hertz_get ()
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returns the number of clock ticks per second. On most systems returns the
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value of
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.BI sysconf( _SC_CLK_TCK )
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or assumed to be \fI100\fR. Divide certain values returned in the
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in the \fI/proc\fR filesystem by this value to convert from ticks to seconds.
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.BR procps_loadavg ()
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Fetches the system load average and puts the 1, 5 and 15 minute averages into
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the locations in the given pointers. If the relevant pointer is \fINULL\fR then
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.BR procps_loadavg ()
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will not set that value.
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.BR procps_pid_length ()
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Returns the maximum string length for a PID on the system. For example, if the largest
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possible PID value on was 123, then the length would be 3. If the file
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\fI/proc/sys/kernel/pid_max\fR is unreadable, the value is assumed to be \fI5\fR.
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.BR procps_linux_version ()
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returns the current Linux version as an integer. On non-Linux systems that
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have an emulated proc filesystem this function returns the version of the
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Linux emulation instead.
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The Linux version consists of a triple of positive integers representing
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the major, minor and patch versions of the kernel.
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.PP
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The library provides 3 macros for separating out the components.
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.RS 4
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.TP 1.2i
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.BR LINUX_VERSION_MAJOR (ver)
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Extract the major component from the given version integer.
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.TP
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.BR LINUX_VERSION_MINOR (ver)
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Extract the minor component from the given version integer.
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.TP
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.BR LINUX_VERSION_PATCH (ver)
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Extract the patch component from the given version integer.
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.RE
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.PP
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To encode a given Linux version, such as using it to compare against the current
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version, use the following macro:
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.TP
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.BI LINUX_VERSION( major , minor , patch )
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.SH RETURN VALUE
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For
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.BR procps_cpu_count "() , " procps_hertz_get "() and " procps_pid_length ()
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see the \fBDESCRIPTION\fR section for return values.
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.BR procps_loadavg ()
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returns 0 on success. On failure, it
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returns a negative integer to one of the values defined below.
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.TP
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.B -ERANGE
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Unable to parse the loadavg file.
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.PP
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.BR procps_linux_version ()
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returns a positive integer encoding the Linux version if successful. Otherwise
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returns a negative integer to one of the values defined below.
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.TP
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.B -EIO
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The procps library was unable to read the osrelease file.
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.TP
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.B -ERANGE
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Unable to parse the osrelease file.
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.PP
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.BR procps_linux_version ()
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may also return any (negated) value that \fBfopen\fR() may set errno to.
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.SH FILES
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.TP
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.I /proc/loadavg
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The raw values for load average.
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.TP
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.I /proc/sys/kernel/osrelease
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Contains the release version of the Linux kernel or proc filesystem.
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.TP
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.I /proc/sys/kernel/pid_max
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Contains the value at which PIDs wrap around, one greater than the maximum PID value.
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.SH BUGS
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Due to the way the three numbers are encoded into a single integer,
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.BR procps_linux_version ()
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and the associated macros assume 255 for the maximum value for the
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minor and patch level and 32767 (hex 0x7fff) for the maximum value
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for the major version. In other words, when Linux v 32768.0.0 comes
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out, this function will break.
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.\" Maj/6yr - In 7452 we'll think of something
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.SH SEE ALSO
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.BR fopen (3),
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.BR sysconf (3),
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.BR proc (5).
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