The hyphen shall not be used as the first character of a portable filename.

"Portable pathname character set" - same as portable filename character set with the addition of the slash character.

According to POSIX.1, the encoding of the portable filename character set is not specified, but the encoding must be unique.

The X Window System assumes that the portable filename character set encoding is identical on all machines in a networked computing environment.

Extended characters may be used in portable filenames as long as there is mutual agreement between these users, even though, technically, this would result in noncompliant use. An optional extension of POSIX.1 may evolve which permits extended characters in portable filenames.

Nothing in POSIX.1 is intended to preclude the use of extended characters where interchange is not required or where mutial agreement is obtained.

"portable filename" - a filename shared by one or more users or applications, often between different systems in a networked computing environment.

"fully portable filename" - a filename consisting of no more than _POSIX_NAME_MAX characters takenn from the portable filename character set.

A compliant POSIX.1 system requires that a portable filename be composed only of characters from the portable filename character set.

POSIX.1 recommends that portable filenames be composed only of characters from the portable filename character set.

POSIX.1 has no reserved filenames.

case folding - the process of treating upper and lower case alphabetic characters as identical.

POSIX.1 does not allow case folding in portable filenames. _POSIX_NAME_MAX - symbol defined in limits.h giving the smallest possible value of NAME_MAX. Currently defined to be 14.

NAME_MAX - symbol defined in limits.h, maximum number of bytes in a filename excluding the terminating null. Must be >= _POSIX_NAME_MAX.

filename - A name consisting of 1 to {NAME_MAX} bytes used to name a file. The charactes composing the name may be selected from the set of all character values excluding the slash character and the null character.

pathname component - same as filename.

reserved filename - one of a list of filenames used in historical implementations such as . and .. and core and /etc/passwd not recommended for use in applications.

pathname - A string that is used to identify a file, consisting of, at most {PATH_MAX} bytes, including the terminating null character. It has an optional beginning slash, follwoed by zero or more filenames separated by slashes. If the path name refers to a directory, it may also have one or more trailing slashes. Multiple successive slashes are considered to be the same as one slash.