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

The source code file is copyright 2024, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

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Function list (Bold in this list means a function is not static)

/* 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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