The POSIX.1 standard specifies a number of parameters that describe the
limitations of the file system. It's possible for the system to have a
fixed, uniform limit for a parameter, but this isn't the usual case. On
most systems, it's possible for different file systems (and, for some
parameters, even different files) to have different maximum limits. For
example, this is very likely if you use NFS to mount some of the file
systems from other machines.
Each of the following macros is defined in limits.h only if the
system has a fixed, uniform limit for the parameter in question. If the
system allows different file systems or files to have different limits,
then the macro is undefined; use pathconf or fpathconf to
find out the limit that applies to a particular file. See Pathconf.
Each parameter also has another macro, with a name starting with
`_POSIX', which gives the lowest value that the limit is allowed to
have on any POSIX system. See File Minimums.
— Macro: int LINK_MAX
The uniform system limit (if any) for the number of names for a given
file. See Hard Links.
— Macro: int MAX_CANON
The uniform system limit (if any) for the amount of text in a line of
input when input editing is enabled. See Canonical or Not.
— Macro: int MAX_INPUT
The uniform system limit (if any) for the total number of characters
typed ahead as input. See I/O Queues.
— Macro: int NAME_MAX
The uniform system limit (if any) for the length of a file name component.
— Macro: int PATH_MAX
The uniform system limit (if any) for the length of an entire file name (that
is, the argument given to system calls such as open).
— Macro: int PIPE_BUF
The uniform system limit (if any) for the number of bytes that can be
written atomically to a pipe. If multiple processes are writing to the
same pipe simultaneously, output from different processes might be
interleaved in chunks of this size. See Pipes and FIFOs.
These are alternative macro names for some of the same information.
— Macro: int MAXNAMLEN
This is the BSD name for NAME_MAX. It is defined in
dirent.h.
— Macro: int FILENAME_MAX
The value of this macro is an integer constant expression that
represents the maximum length of a file name string. It is defined in
stdio.h.
Unlike PATH_MAX, this macro is defined even if there is no actual
limit imposed. In such a case, its value is typically a very large
number. This is always the case on the GNU system.
Usage Note: Don't use FILENAME_MAX as the size of an
array in which to store a file name! You can't possibly make an array
that big! Use dynamic allocation (see Memory Allocation) instead.
Published under the terms of the GNU General Public License
