access: Testing File Permissions

• The access system call determines whether the calling process has access permission to a file.
• It can check any combination of read, write, and execute permission, and it can also check for a file's existence.
• The access call takes two arguments.
• The return value is 0 if the process has all the specified permissions.
• If the file exists but the calling process does not have the specified permissions, access returns 1 and sets errno to EACCES (or EROFS, if write permission was requested for a file on a read-only file system).
• The http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/check-access.c program shown in Fig. 8.1 uses access to check for a file's existence and to determine read and write permissions.

  Figure 8.1: Check File Access Permissions.

  

  $ ./check-access /mnt/cdrom/README