This is procpri/sched_set.c (Listing 35-2, page 743), an example program file from the book, The Linux Programming Interface.

The source code file is copyright 2010, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

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In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.

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/* sched_set.c

   Usage: sched_set policy priority pid...

   Sets the policy and priority of all process specified by the 'pid' arguments.

   See also sched_view.c.

   The distribution version of this code is slightly different from the code
   shown in the book in order to better fix a bug that was present in the code
   as originally shown in the book. See the erratum for page 743
#include <sched.h>
#include "tlpi_hdr.h"
main(int argc, char *argv[])
    int j, pol;
    struct sched_param sp;

    if (argc < 3 || strchr("rfo"
#ifdef SCHED_BATCH              /* Linux-specific */
#ifdef SCHED_IDLE               /* Linux-specific */
                , argv[1][0]) == NULL)
        usageErr("%s policy priority [pid...]\n"
                "    policy is 'r' (RR), 'f' (FIFO), "
#ifdef SCHED_BATCH              /* Linux-specific */
                "'b' (BATCH), "
#ifdef SCHED_IDLE               /* Linux-specific */
                "'i' (IDLE), "
                "or 'o' (OTHER)\n",

    pol = (argv[1][0] == 'r') ? SCHED_RR :
                (argv[1][0] == 'f') ? SCHED_FIFO :
#ifdef SCHED_BATCH              /* Linux-specific, since kernel 2.6.16 */
                (argv[1][0] == 'b') ? SCHED_BATCH :
#ifdef SCHED_IDLE               /* Linux-specific, since kernel 2.6.23 */
                (argv[1][0] == 'i') ? SCHED_IDLE :

    sp.sched_priority = getInt(argv[2], 0, "priority");

    for (j = 3; j < argc; j++)
        if (sched_setscheduler(getLong(argv[j], 0, "pid"), pol, &sp) == -1)



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