xattr_view.c

/*************************************************************************\
*                  Copyright (C) Michael Kerrisk, 2022.                   *
*                                                                         *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU General Public License as published by the   *
* Free Software Foundation, either version 3 or (at your option) any      *
* later version. This program is distributed without any warranty.  See   *
* the file COPYING.gpl-v3 for details.                                    *
\*************************************************************************/

/* view_xattr.c

   Display the extended attributes of a file.

   This program is Linux (2.6 and later) specific.

   See also t_setxattr.c.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/xattr.h>
#include <unistd.h>

#define XATTR_SIZE 10000

static void
usageError(char *progName)
{
    fprintf(stderr, "Usage: %s [-x] file...\n", progName);
    exit(EXIT_FAILURE);
}

int
main(int argc, char *argv[])
{
    char list[XATTR_SIZE], value[XATTR_SIZE];
    ssize_t listLen, valueLen;
    int ns, j, k, opt;
    int hexDisplay;

    hexDisplay = 0;
    while ((opt = getopt(argc, argv, "x")) != -1) {
        switch (opt) {
        case 'x': hexDisplay = 1;       break;
        case '?': usageError(argv[0]);
        }
    }

    if (optind >= argc)
        usageError(argv[0]);

    for (j = optind; j < argc; j++) {
        listLen = listxattr(argv[j], list, XATTR_SIZE);
        if (listLen == -1) {
            fprintf(stderr,"listxattr failed: %m");
            exit(EXIT_FAILURE);
        }

        printf("%s:\n", argv[j]);

        /* Loop through all EA names, displaying name + value */

        for (ns = 0; ns < listLen; ns += strlen(&list[ns]) + 1) {
            printf("        name=%s; ", &list[ns]);

            valueLen = getxattr(argv[j], &list[ns], value, XATTR_SIZE);
            if (valueLen == -1) {
                printf("couldn't get value");
            } else if (!hexDisplay) {
                printf("value=%.*s", (int) valueLen, value);
            } else {
                printf("value=");
                for (k = 0; k < valueLen; k++)
                    printf("%02x ", (unsigned char) value[k]);
            }

            printf("\n");
        }

        printf("\n");
    }

    exit(EXIT_SUCCESS);
}