SAS/C Library Reference, Vol. 1

access -- Test for File Existence and Access Privileges

SYNOPSIS

 #include <unistd.h>

 int access(const char *path, int amode);

SAS/C enables the header file <fcntl.h> to be included in place of <unistd.h>.

DESCRIPTION

The access function determines if a file exists and if that file can be read or written. path points to a filename of any style. The type of access tested for is given by amode, which can be the sum of one or more of the following symbols:

F_OK: indicates that the file exists.
R_OK: indicates read access.
W_OK: indicates write access.
X_OK: indicates execute access.

Use the bitwise inclusive OR to test several access modes simultaneously. You cannot use OR to specify F_OK with another symbol. X_OK is ignored, except for OpenEdition hierarchical file system (HFS) files.

RETURN VALUE

The access function returns 0 if the file exists and if the type (or types) of access specified by amode is allowed. If the file does not exist or the specified type of access is not allowed, - 1 is returned.

CAUTION

MVS A sequential file exists if it contains any data (as recorded in the VTOC). For more information on MVS file existence, see I/O Functions .

A 0 return value from access does not necessarily mean that the file can be opened, even if the type of access is allowed. For example, a file may fail to open because incorrect DCB information is specified. A - 1 return value always indicates that the file cannot be opened with the specified type of access.

CMS If the filemode is not specified, * is used, unless amode indicates that write access is to be tested. In this case, A1 is used as the filemode.

If the filename is in xed style and XEDIT is not active or the file is not found in XEDIT, the file is searched for on disk. Write access (W_OK ) is not allowed for xed or sfd style files.

Under CMS, the access function cannot be used with VSAM files.

IMPLEMENTATION

Any amode value can be tested for any device type. If the mode is not valid for a device, - 1 is returned.

EXAMPLES

  #include <fcntl.h>
  #include <stdio.h>

  main()
  {
     int rc;

        /* Does the program have read and write access to the */
        /*  TSO ISPF profile dataset?                         */
     rc = access("tso:ispf.profile", R_OK + W_OK);

     if (rc == 0)
        puts("Read and write access exists.");
     else
        puts("Read and write access does not exist.");

        /* Does the member DATA1 exist in the partitioned     */
        /*  dataset referred to by the ddname MYPROG?         */
     rc = access("tso:myprog(data1)", 0);

     if (rc == 0)
        puts("File exists.");
     else
        puts("File does not exist.");

        /* Can SYS1.PARMLIB be updated?                       */
     rc = access("dsn:sys1.parmlib", W_OK);

     if (rc == 0)
        puts("Yes, SYS1.PARMLIB can be updated.");
     else
        puts("SYS1.PARMLIB cannot be updated.");
  }

RELATED FUNCTIONS

cmsstat, stat