Stash away shared memory utility

util/shm/shmcat.c

+/*
+ * Copyright (c) 2014 Nicholas J. Kain
+ * Licensed under 2-clause BSD.
+ * Prints the contents of a SysV shm segment.
+ *
+ * Build: gcc -O2 -std=gnu99 shmcat.c -o shmcat
+ * Usage: shmcat <shmid>
+ *
+ * Get the shmid by using 'ipcs -m'.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <limits.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+
+int main(int argc, char *argv[])
+{
+    if (argc < 2) {
+        printf("Need to specify a shmid as first argument.\n");
+        return -1;
+    }
+    char *eptr;
+    long shmidl = strtol(argv[1], &eptr, 0);
+    if (((shmidl == LONG_MIN || shmidl == LONG_MAX) && errno == ERANGE)
+        || eptr == argv[1]) {
+        printf("shmid out of range or not a number: '%s'\n", argv[1]);
+        return -1;
+    }
+    if (shmidl < 0 || shmidl > INT_MAX) {
+        printf("shmid out of range: '%lu'\n", shmidl);
+        return -1;
+    }
+    int shmid = shmidl;
+    struct shmid_ds ds;
+    int err = shmctl(shmid, IPC_STAT, &ds);
+    if (err < 0) {
+        printf("shmctl() failed: %s\n", strerror(errno));
+        return -1;
+    }
+    size_t shm_bytes = ds.shm_segsz;
+    printf("shmid=%i bytes=%zu\n-=-=-=-=-=-\n", shmid, shm_bytes);
+    void *s = shmat(shmid, NULL, SHM_RDONLY);
+    if (s == (void *)-1) {
+        printf("shmat() failed: %s\n", strerror(errno));
+        return -1;
+    }
+#ifdef XXX
+    char sbuf[32];
+    memset(sbuf, 0, sizeof sbuf);
+    size_t si = 0;
+    printf("\n%8.8zX  ", si);
+    for (si = 0; si < shm_bytes; ++si) {
+        size_t sis = si % 16;
+        if (si && si % 16 == 0) {
+            printf(" ");
+            for (size_t i = 0; i < 16; ++i) {
+                printf("%c", isprint(sbuf[i]) ? sbuf[i] : '.');
+            }
+            memset(sbuf, 0, sizeof sbuf);
+            printf("\n%8.8zX  ", si);
+        }
+        sbuf[sis] = ((char *)s)[si];
+        printf("%2.2X ", sbuf[sis]);
+    }
+    if (si) {
+        size_t sis = si % 16;
+        sis = sis ? sis : 16;
+        for (size_t i = sis; i < 16; ++i)
+            printf("   ");
+        printf(" ");
+        for (size_t i = 0; i < sis; ++i) {
+            printf("%c", isprint(sbuf[i]) ? sbuf[i] : '.');
+        }
+        memset(sbuf, 0, sizeof sbuf);
+        printf("\n");
+    }
+    printf("\n");
+#else
+    size_t si = 0;
+    for (si = 0; si < shm_bytes; ++si) 
+    {
+        if (((char*)s)[si] != 0)
+	    printf("%lx:%u\n", si, (unsigned char)((char *)s)[si]);
+    }
+
+#endif
+
+    err = shmdt(s);
+    if (err < 0) {
+        printf("shmdt() failed: %s\n", strerror(errno));
+        return -1;
+    }
+    return 0;
+}