svsem/svsem_op.c

/* svsem_op.c

   Perform groups of operations on a System V semaphore set.

   Usage as shown in usageError().
*/
#include <sys/types.h>
#include <sys/sem.h>
#include <ctype.h>
#include "curr_time.h"          /* Declaration of currTime() */
#include "tlpi_hdr.h"

#define MAX_SEMOPS 1000         /* Maximum operations that we permit for
                                   a single semop() */

static void
usageError(const char *progName)
{
    fprintf(stderr, "Usage: %s semid op[,op...] ...\n\n", progName);
    fprintf(stderr, "'op' is either: <sem#>{+|-}<value>[n][u]\n");
    fprintf(stderr, "            or: <sem#>=0[n]\n");
    fprintf(stderr, "       \"n\" means include IPC_NOWAIT in 'op'\n");
    fprintf(stderr, "       \"u\" means include SEM_UNDO in 'op'\n\n");
    fprintf(stderr, "The operations in each argument are "
                    "performed in a single semop() call\n\n");
    fprintf(stderr, "e.g.: %s 12345 0+1,1-2un\n", progName);
    fprintf(stderr, "      %s 12345 0=0n 1+1,2-1u 1=0\n", progName);
    exit(EXIT_FAILURE);
}

/* Parse comma-delimited operations in 'arg', returning them in the
   array 'sops'. Return number of operations as function result. */

static int
parseOps(char *arg, struct sembuf sops[])
{
    char *comma, *sign, *remaining, *flags;
    int numOps;                 /* Number of operations in 'arg' */

    for (numOps = 0, remaining = arg; ; numOps++) {
        if (numOps >= MAX_SEMOPS)
            cmdLineErr("Too many operations (maximum=%d): \"%s\"\n",
                        MAX_SEMOPS, arg);

        if (*remaining == '\0')
            fatal("Trailing comma or empty argument: \"%s\"", arg);
        if (!isdigit((unsigned char) *remaining))
            cmdLineErr("Expected initial digit: \"%s\"\n", arg);

        sops[numOps].sem_num = strtol(remaining, &sign, 10);

        if (*sign == '\0' || strchr("+-=", *sign) == NULL)
            cmdLineErr("Expected '+', '-', or '=' in \"%s\"\n", arg);
        if (!isdigit((unsigned char) *(sign + 1)))
            cmdLineErr("Expected digit after '%c' in \"%s\"\n", *sign, arg);

        sops[numOps].sem_op = strtol(sign + 1, &flags, 10);

        if (*sign == '-')                       /* Reverse sign of operation */
            sops[numOps].sem_op = - sops[numOps].sem_op;
        else if (*sign == '=')                  /* Should be '=0' */
            if (sops[numOps].sem_op != 0)
                cmdLineErr("Expected \"=0\" in \"%s\"\n", arg);

        sops[numOps].sem_flg = 0;
        for (;; flags++) {
            if (*flags == 'n')
                sops[numOps].sem_flg |= IPC_NOWAIT;
            else if (*flags == 'u')
                sops[numOps].sem_flg |= SEM_UNDO;
            else
                break;
        }

        if (*flags != ',' && *flags != '\0')
            cmdLineErr("Bad trailing character (%c) in \"%s\"\n", *flags, arg);

        comma = strchr(remaining, ',');
        if (comma == NULL)
            break;                              /* No comma --> no more ops */
        else
            remaining = comma + 1;
    }

    return numOps + 1;
}

int
main(int argc, char *argv[])
{
    struct sembuf sops[MAX_SEMOPS];
    int ind, nsops;

    if (argc < 2 || strcmp(argv[1], "--help") == 0)
        usageError(argv[0]);

    for (ind = 2; argv[ind] != NULL; ind++) {
        nsops = parseOps(argv[ind], sops);

        printf("%5ld, %s: about to semop()  [%s]\n", (long) getpid(),
                currTime("%T"), argv[ind]);

        if (semop(getInt(argv[1], 0, "semid"), sops, nsops) == -1)
            errExit("semop (PID=%ld)", (long) getpid());

        printf("%5ld, %s: semop() completed [%s]\n", (long) getpid(),
                currTime("%T"), argv[ind]);
    }

    exit(EXIT_SUCCESS);
}