how to use attr_multi() properly ?

[VR <vreikine@xxxxxxxxx>]

Hi,
I am trying to use attr_multi() in my small application on Linux.
It's ArchLinux on Intel laptop
Kernel is 2.6.23
filesystem is XFS
getfattr --version returns 2.4.39

Basically, I want to use EA to store environment variables for an
application - e.g. 'ant' needs ANT_HOME and ANT_LIB , 'jetty' needs
JETTY_HOME etc.
For any given file I want to get EA of "user.env.n" where n is 0...8 ,
so I allocated memory, created attr_multi_op_t array, filled it up
with proper values etc.
Then I make a call to attr_multi() and check the return code. I am
getting the EA values ok, but my question is about return code, errno
and am_error in attr_multiop_t .

Here is the snippets of my code - it's rather long so I cut some pieces out.

const char *ea_env = "env";

int main(int argc, char **argv)
{
        int rc;
        int i,j,k,l,m,n;
        attr_multiop_t ea[EA_SIZE];
        char *ea_buf[EA_SIZE];
        char *ea_argname[EA_MAX_ARG];
        char *ea_envname[EA_MAX_ENV];
        char *ea_name, *ea_path, *ea_ext, *ea_self, *ea_selfs;
        char *tmpval, *tmpvall , *tmpvalll;

        /* initialization */
        rc = 0;                 /* return code */
        
        /* common params for all EA */
        for ( i = 0; i < EA_SIZE; i++) {
                ea[i].am_opcode = ATTR_OP_GET ;
                ea[i].am_error = 0;
                ea[i].am_flags = 0;
        }
/*
. skipped not important stuff -
*/

        /* names are in form "env.#" */
        n = strlen(ea_env) + 2 + 1 ;
        /* limit number of args to 16 - 1 hex digit */
        if ((tmpval = malloc( n * (EA_MAX_ENV & 0xF))) == NULL ) {
                perror("malloc: failed to allocate memory for ea_envname") ;
                _exit(errno);
        }
        memset(tmpval, 0, (n * EA_MAX_ARG & 0xF)) ;

        for ( i = 0; i < EA_MAX_ENV & 0xF ; i++) {
                ea_envname[i] = tmpval;
                snprintf(ea_envname[i], n, "%s.%x", ea_env, i) ;
                tmpval +=n ;
                ea_buf[EA_ENV+i] = malloc(EA_MAX_ARGLEN) ;
                if (ea_buf[EA_ENV+i] == NULL) {
                        perror("malloc: failed to allocate memory for ea_env" );
                        _exit(errno);
                }
                ea[EA_ENV+i].am_attrname = ea_envname[i];
                ea[EA_ENV+i].am_attrvalue = ea_buf[EA_ENV+i];
                ea[EA_ENV+i].am_length = EA_MAX_ARGLEN ;

        }

        if (argc > 1) {
                printf("filename %s:\n",argv[1]);
                rc = attr_multi( argv[1], ea , EA_SIZE, 0);
                if ( rc != 0) {
                        printf("rc= %d, errno = %d\n", rc, errno);
                }
                for ( i=0 ; i < EA_SIZE ; i++) {
                        if (ea[i].am_error == 0 && (k = 
strlen(ea[i].am_attrvalue)) ==
ea[i].am_length) {
                                printf(" %d:\t%s\t%s\t%d\t%d\n", i, 
ea[i].am_attrname,
ea[i].am_attrvalue, ea[i].am_length, ea[i].am_error) ;
/* skip not important stuff */
                        }
               }
         }
/* skip not important stuff */
return rc;
}

I use gcc 4.2.2 and compile it with "-lattr"
I use "setfattr" to set EA on a test file and let's say I set
user.env.0 and user.env.1 to some values.
I can see those values with "getfattr -d" and I can see them with my
small command but am_error is always 0 - for all " env.#" no matter if
they set or not. I have to use 'strlen()' and compare it to am_length
to check if there is value of EA.
and I am getting "rc = -1" and "errno = -22" (negative 22?), or "rc =
-1" and "errno = 61" depending on EA I set or not set on a test file.
I'd rather have am_error set to proper value if there is no data and
check.



Could you please advise on how to call attr_multi() to get a bunch of
attributes at once properly, or is it better just do attr_get() in a
loop ?

Sincerely,
Vladimir