An example code is provided for listxattr and getxattr. Changes from version 1: As Michael correctly pointed out, the buffer length returned by listxattr does not contain any byte after the 0x00 indicating the end of the last list entry. Furthermore getxattr does not append 0x00. Signed-off-by: Heinrich Schuchardt <xypron.glpk@xxxxxx> --- man2/listxattr.2 | 141 ++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 140 insertions(+), 1 deletion(-) diff --git a/man2/listxattr.2 b/man2/listxattr.2 index a67592f..3fa6d20 100644 --- a/man2/listxattr.2 +++ b/man2/listxattr.2 @@ -1,5 +1,6 @@ .\" Copyright (C) Andreas Gruenbacher, February 2001 .\" Copyright (C) Silicon Graphics Inc, September 2001 +.\" Copyright (C) 2015 Heinrich Schuchardt <xypron.glpk@xxxxxx> .\" .\" %%%LICENSE_START(GPLv2+_DOC_FULL) .\" This is free documentation; you can redistribute it and/or @@ -22,7 +23,7 @@ .\" <http://www.gnu.org/licenses/>. .\" %%%LICENSE_END .\" -.TH LISTXATTR 2 2014-02-06 "Linux" "Linux Programmer's Manual" +.TH LISTXATTR 2 2015-02-09 "Linux" "Linux Programmer's Manual" .SH NAME listxattr, llistxattr, flistxattr \- list extended attribute names .SH SYNOPSIS @@ -150,6 +151,144 @@ These system calls are Linux-specific. .\" and the SGI XFS development team, .\" .RI < linux-xfs@xxxxxxxxxxx >. .\" Please send any bug reports or comments to these addresses. +.SH EXAMPLE +The following program demonstrates the usage of +.BR listxattr () +and +.BR getxattr (2). +For a path provided, it lists all extended file attributes and their values. + +The following output was recorded when first creating a file, setting +some extended file attributes, and then listing them with the example code. + +.SS Example output +.in +4n +.nf +$ touch /tmp/foo +$ setfattr -n user.fred -v chocolate /tmp/foo +$ setfattr -n user.frieda -v bar /tmp/foo +$ setfattr -n user.empty /tmp/foo +$ ./listxattr /tmp/foo +user.fred: chocolate +user.frieda: bar +user.empty: <no value> +.fi +.in +.SS Program source +.nf +#include <malloc.h> +#include <stdio.h> +#include <stdlib.h> +#include <attr/xattr.h> +#include <sys/types.h> + +int +main(int argc, char *argv[]) +{ + ssize_t keylen, vallen; + char *key, *p, *val; + int i; + + if (argc != 2) { + fprintf(stderr, "usage: %s path\\n", argv[0]); + exit(EXIT_FAILURE); + } + + /* + * determine the length of the buffer needed + */ + keylen = listxattr(argv[1], NULL, 0); + if (keylen == \-1) { + perror("listxattr"); + exit(EXIT_FAILURE); + } + if (keylen == 0) { + printf("%s has no attibutes.\\n", argv[1]); + exit(EXIT_SUCCESS); + } + + /* + * allocate the buffer + */ + key = malloc(keylen); + if (key == NULL) { + perror("malloc"); + exit(EXIT_FAILURE); + } + + /* + * copy the attribute list to the buffer + */ + keylen = listxattr(argv[1], key, keylen); + if (keylen == \-1) { + perror("listxattr"); + exit(EXIT_FAILURE); + } + + /* + * The end of the list is marked by zero terminated string + * of length zero. + */ + p = key; + while (keylen > 0) { + + /* + * output attribute name + */ + printf("%s: ", p); + + /* + * determine length of value + */ + vallen = getxattr(argv[1], p, NULL, 0); + if (vallen == \-1) + perror("getxattr"); + + if (vallen > 0) { + /* + * allocate value buffer + * one extra byte to append 0x00 + */ + ++vallen; + val = malloc(vallen); + if (val == NULL) { + perror("malloc"); + exit(EXIT_FAILURE); + } + + /* + * read value to buffer + */ + vallen = getxattr(argv[1], p, val, vallen); + if (vallen == \-1) + perror("getxattr"); + else { + /* + * output attribute value + */ + val[vallen] = 0; + printf("%s", val); + } + + free(val); + } else + printf("<no value>"); + + printf("\\n"); + + /* + *forward to next attribute name + */ + while(*++p) + \-\-keylen; + ++p; + keylen \-= 2; + } + + free(key); + exit(EXIT_SUCCESS); +} +.fi .SH SEE ALSO .BR getfattr (1), .BR setfattr (1), -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
