glossary.9 (2010 09)
p
glossary(9) glossary(9)
password
A string of ASCII characters used to verify the identity of a user. Passwords can be associated with users
and groups. If a user has a password, it is automatically encrypted and entered in the second field of that
user’s line in the
/etc/passwd file. A user can create or change his or her own password by using the
passwd (1) command.
path name
A sequence of directory names separated by slashes, and ending with any file name. All file names except
the last in the sequence must be directories. If a path name begins with a slash (
/), it is an absolute
path name; otherwise, it is a relative path name. A path name defines the path to be followed through
the hierarchical file system in order to find a particular file.
More precisely, a path name is a null-terminated character string constructed as follows:
<path-name>::=<file-name><path-prefix><file-name>
/
<path-prefix>::=<rtprefix>/<rtprefix>
<rtprefix>::=<dirname>
/<rtprefix><dirname>/
where <file-name> is a string of one or more characters other than the ASCII slash and null, and <dir-
name> is a string of one or more characters (other than the ASCII slash and null) that names a directory.
File and directory names can consist of up to 14 characters on systems supporting short file names and up
to 255 characters on systems supporting long file names.
A slash (
/) by itself names the root directory. Two or more slashes in succession (
////...) are treated
as a single slash.
Unless specifically stated otherwise, the null or zero-length path name is treated as though it named a
nonexistent file.
path name resolution
The process that resolves a path name to a particular file in a file hierarchy. Multiple path names can
resolve to the same file, depending on whether resolution is sought in absolute or relative terms (see
below). Each file name in the path name is located in the directory specified by its predecessor (for exam-
ple, in the path name fragment
a/b,fileb is located in directory a). Path name resolution fails if this
cannot be accomplished.
If the path name begins with a slash, the predecessor of the first file name in the path name is understood
to be the root directory of the process, and the path name is referred to as an absolute path name.If
the path name does not begin with a slash, the predecessor of the first file name of the path name is
understood to be the current working directory of the process, and the path name is referred to as a rela-
tive path name. A path name consisting of a single slash resolves to the root directory of the process.
path prefix
A path name with an optional ending slash that refers to a directory.
permission bits
The nine least-significant bits of a file’s mode are referred to as file permission bits. These bits deter-
mine read, write, and execute permissions for the file’s owner, the file’s group, and all others. The bits
are divided into three parts: owner, group and other. Each part is used with the corresponding file class
of processes. The bits are contained in the file mode, as described in stat (5). The detailed usage of the
file permission bits in access decisions is described in file access permissions.
persistent device special file
A device file for mass storage devices, which is associated with a LUN hardware path, and thus tran-
sparently supports agile addressing and multipathing. In other words, a persistent device special file is
unchanged if the LUN is moved from one host bus adapter (HBA) to another, moved from one switch/hub
port to another, presented via a different target port to the host, or configured with multiple hardware
paths. See intro (7) for more information on device special files.
PIC
See position-independent code.
pipe
An interprocess I/O channel used to pass data between two processes. It is commonly used by the shell to
transfer data from the standard output of one process to the standard input of another. On a command
line, a pipe is signaled by a vertical bar (
|). Output from the command to the left of the vertical bar is
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