The following directories shall exist on conforming systems and conforming applications shall make use of them only as described. Strictly conforming applications shall not assume the ability to create files in any of these directories, unless specified below.
The following directory shall exist on conforming systems and shall be used as described:
The following files shall exist on conforming systems and shall be both readable and writable:
The following file shall exist on conforming systems and need not be readable or writable:
The utilities in the Shell and Utilities volume of POSIX.1-2024 historically have been implemented on a wide range of terminal types, but a conforming implementation need not support all features of all utilities on every conceivable terminal. POSIX.1-2024 states which features are optional for certain classes of terminals in the individual utility description sections. The implementation shall document in the system documentation which terminal types it supports and which of these features and utilities are not supported by each terminal.
When a feature or utility is not supported on a specific terminal type, as allowed by POSIX.1-2024, and the implementation considers such a condition to be an error preventing use of the feature or utility, the implementation shall indicate such conditions through diagnostic messages or exit status values or both (as appropriate to the specific utility description) that inform the user that the terminal type lacks the appropriate capability.
POSIX.1-2024 uses a notational convention based on historical practice that identifies some of the control characters defined in
7.3.1 LC_CTYPE in a manner easily remembered by users on many
terminals. The correspondence between this "<control>-char" notation and the actual control characters is shown in
the following table. When POSIX.1-2024 refers to a character by its <control>-name, it is referring to the actual
control character shown in the Value column of the table, which is not necessarily the exact control key sequence on all terminals.
Some terminals have keyboards that do not allow the direct transmission of all the non-alphanumeric characters shown. In such
cases, the system documentation shall describe which data sequences transmitted by the terminal are interpreted by the system as
representing the special characters.
Table: Control Character Names
Name |
Value |
Name |
Value |
---|---|---|---|
<control>-A |
<SOH> |
<control>-Q |
<DC1> |
<control>-B |
<STX> |
<control>-R |
<DC2> |
<control>-C |
<ETX> |
<control>-S |
<DC3> |
<control>-D |
<EOT> |
<control>-T |
<DC4> |
<control>-E |
<ENQ> |
<control>-U |
<NAK> |
<control>-F |
<ACK> |
<control>-V |
<SYN> |
<control>-G |
<BEL> |
<control>-W |
<ETB> |
<control>-H |
<BS> |
<control>-X |
<CAN> |
<control>-I |
<HT> |
<control>-Y |
<EM> |
<control>-J |
<LF> |
<control>-Z |
<SUB> |
<control>-K |
<VT> |
<control>-[ |
<ESC> |
<control>-L |
<FF> |
<control>-\ |
<FS> |
<control>-M |
<CR> |
<control>-] |
<GS> |
<control>-N |
<SO> |
<control>-^ |
<RS> |
<control>-O |
<SI> |
<control>-_ |
<US> |
<control>-P |
<DLE> |
<control>-? |
<DEL> |
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