31.8 Minimum Values for File System Limits

Here are the names for the POSIX minimum upper bounds for some of the above parameters. The significance of these values is that you can safely push to these limits without checking whether the particular system you are using can go that far. In most cases GNU systems do not have these strict limitations. The actual limit should be requested if necessary.

_POSIX_LINK_MAX

The most restrictive limit permitted by POSIX for the maximum value of a file's link count. The value of this constant is 8; thus, you can always make up to eight names for a file without running into a system limit.

_POSIX_MAX_CANON

The most restrictive limit permitted by POSIX for the maximum number of bytes in a canonical input line from a terminal device. The value of this constant is 255.

_POSIX_MAX_INPUT

The most restrictive limit permitted by POSIX for the maximum number of bytes in a terminal device input queue (or typeahead buffer). See Input Modes. The value of this constant is 255.

_POSIX_NAME_MAX

The most restrictive limit permitted by POSIX for the maximum number of bytes in a file name component. The value of this constant is 14.

_POSIX_PATH_MAX

The most restrictive limit permitted by POSIX for the maximum number of bytes in a file name. The value of this constant is 256.

_POSIX_PIPE_BUF

The most restrictive limit permitted by POSIX for the maximum number of bytes that can be written atomically to a pipe. The value of this constant is 512.

SYMLINK_MAX

Maximum number of bytes in a symbolic link.

POSIX_REC_INCR_XFER_SIZE

Recommended increment for file transfer sizes between the POSIX_REC_MIN_XFER_SIZE and POSIX_REC_MAX_XFER_SIZE values.

POSIX_REC_MAX_XFER_SIZE

Maximum recommended file transfer size.

POSIX_REC_MIN_XFER_SIZE

Minimum recommended file transfer size.

POSIX_REC_XFER_ALIGN

Recommended file transfer buffer alignment.