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libwchar2 0.0.10
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__waccess - check user's permissions for a file__
The waccess() checks whether the calling process can access the file path- name. If pathname is a symbolic link, it is dereferenced.
The mode specifies the accessibility check(s) to be performed, and is either the value F_OK, or a mask consisting of the bitwise OR of one or more of R_OK, W_OK, and X_OK. F_OK tests for the existence of the file. R_OK, W_OK, and X_OK test whether the file exists and grants read, write, and execute permissions, respectively.
The check is done using the calling process's real UID and GID, rather than the effective IDs as is done when actually attempting an operation (e.g., open(2)) on the file. Similarly, for the root user, the check uses the set of permitted capabilities rather than the set of effective capabilities; and for non-root users, the check uses an empty set of capabilities.
This allows set-user-ID programs and capability-endowed programs to easily determine the invoking user's authority. In other words, access() does not answer the "can I read/write/execute this file?" question. It answers a slightly different question: "(assuming I'm a setuid binary) can the user who invoked me read/write/execute this file?", which gives set-user-ID programs the possibility to prevent malicious users from causing them to read files which users shouldn't be able to read.
If the calling process is privileged (i.e., its real UID is zero), then an X_OK check is successful for a regular file if execute permission is enabled for any of the file owner, group, or other.
On success, all requested permissions granted, or mode is F_OK and the file exists, return extended status, see access_e enum value:
ISUNK is a UnknownISFIL is a Regular fileISLNK is a Symbolic linkISDIR is a DirectoryOn error, at least one bit in mode asked for a permission that is denied, or mode is F_OK and the file does not exist, or some other error occurred, -1 is returned, and errno is set appropriately.
1.8.14