The description of listxattr did not point out how that the array of attributes itself is null-terminated. The missing information has been added. Furthermore example code is provided. Signed-off-by: Heinrich Schuchardt <xypron.glpk@xxxxxx> --- man2/listxattr.2 | 144 +++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 139 insertions(+), 5 deletions(-) diff --git a/man2/listxattr.2 b/man2/listxattr.2 index a67592f..05197c4 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 2015-02-08 "Linux" "Linux Programmer's Manual" .SH NAME listxattr, llistxattr, flistxattr \- list extended attribute names .SH SYNOPSIS @@ -95,13 +96,14 @@ size of a buffer which is sufficiently large to hold the list of names. .SS Example The .I list -of names is returned as an unordered array of null-terminated character -strings (attribute names are separated by null bytes (\(aq\\0\(aq)), like this: +of names is returned as a null-terminated unordered array of +null-terminated character strings +(attribute names are separated by null bytes (\(aq\\0\(aq)), like this: .fam C .RS .nf -user.name1\\0system.name1\\0user.name2\\0 +user.name1\\0system.name1\\0user.name2\\0\\0 .fi .RE .fam T @@ -114,7 +116,7 @@ like this: .RS .nf -system.posix_acl_access\\0system.posix_acl_default\\0 +system.posix_acl_access\\0system.posix_acl_default\\0\\0 .fi .RE .fam T @@ -150,6 +152,138 @@ 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 buflen; + char *buf, *p, *val; + + if (argc != 2) { + fprintf(stderr, "usage: %s path\\n", argv[0]); + exit(EXIT_FAILURE); + } + + /* + * determine the length of the buffer needed + */ + buflen = listxattr(argv[1], NULL, 0); + if (buflen == \-1) { + perror("listxattr"); + exit(EXIT_FAILURE); + } + if (buflen == 0) { + printf("%s has no attibutes.\\n", argv[1]); + exit(EXIT_SUCCESS); + } + + /* + * allocate the buffer + */ + buf = malloc(buflen); + if (buf == NULL) { + perror("malloc"); + exit(EXIT_FAILURE); + } + + /* + * copy the attribute list to the buffer + */ + buflen = listxattr(argv[1], buf, buflen); + if (buflen == \-1) { + perror("listxattr"); + exit(EXIT_FAILURE); + } + + /* + * The end of the list is marked by zero terminated string + * of length zero. + */ + p = buf; + while (*p) { + + /* + * output attribute name + */ + printf("%s: ", p); + + /* + * determine length of value + */ + buflen = getxattr(argv[1], p, NULL, 0); + if (buflen == \-1) + perror("getxattr"); + + if (buflen > 0) { + /* + * allocate value buffer + */ + val = malloc(buflen); + if (val == NULL) { + perror("malloc"); + exit(EXIT_FAILURE); + } + + /* + * read value to buffer + */ + buflen = getxattr(argv[1], p, val, buflen); + if (buflen == \-1) + perror("getxattr"); + else + /* + * output attribute value + */ + printf("%s", val); + + free(val); + } else + printf("<no value>"); + + printf("\\n"); + + /* + *forward to next attribute name + */ + while(*++p); + ++p; + } + + free(buf); + exit(EXIT_SUCCESS); +} +.nf +.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
