In the next section, we will cover the
creation of files and directories, so it is important to review the
naming of UNIX files and directories before we begin.
All operating systems have some basic guidelines or conventions that
must be followed. The rules here apply to UNIX files and directories.
Refer to the Figure for a summary of the UNIX file and directory
naming guidelines or conventions.
- Maximum Length - The maximum
length of files and directories combined is 255 alphanumeric
characters.
- Non-alphanumeric characters -
Some alphanumeric characters are allowed - Underscores (_),
hyphens (-), and periods (.) can be used multiple times in a
file or directory name (For Example, Feb.Reports.Sales). While the shell will
allow asterisks (*), ampersands (&), pipes (|), quotes ("
"), and dollar signs ($) to be used in a file name, this is
not recommended, as these characters have special meaning to the
shell.
- File Name Extensions - File
Names may contain one or more extensions. Extensions are usually
appended to files by an application. Extensions are usually one to
three characters that are appended to the end of a file name and
are preceded by a period (.). You may choose to use this
convention when naming files, but it is not a necessary part of a
file name.
- Directory Name Extensions -
Directory names generally do not contain extensions, but there are
no rules against it.
Note: To help distinguish
between files and directories, some site administrators prefer their
users to start filenames with lowercase letters and directory names
with capital letters. They may also recommend including an upper
case letter D_ in the first position or include .dir on the end of
directory names to distinguish them from file names. If no
convention is used to distinguish files from directories, you can
always use the ls -F
command line to visibly show which is which.
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