выполнять команды и открывать, закрывать или копировать файловые дескрипторы (execute commands and open, close, or copy file descriptors)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
exec — execute commands and open, close, or copy file descriptors
Синопсис (Synopsis)
exec [command [argument...]]
Описание (Description)
The exec utility shall open, close, and/or copy file descriptors
as specified by any redirections as part of the command.
If exec is specified without command or arguments, and any file
descriptors with numbers greater than 2 are opened with
associated redirection statements, it is unspecified whether
those file descriptors remain open when the shell invokes another
utility. Scripts concerned that child shells could misuse open
file descriptors can always close them explicitly, as shown in
one of the following examples.
If exec is specified with command, it shall replace the shell
with command without creating a new process. If arguments are
specified, they shall be arguments to command. Redirection
affects the current shell execution environment.
Параметры (Options)
None.
Операнды (Operands)
See the DESCRIPTION.
Стандартный ввод (Stdin)
Not used.
Входные файлы (Input files)
None.
Переменные окружения (Environment variables)
None.
Асинхронные события (Asynchronous events)
Default.
Стандартный вывод (Stdout)
Not used.
Стандартный вывод сообщений (Stderr)
The standard error shall be used only for diagnostic messages.
Выходные файлы (Output files)
None.
Расширенное описание (Extended description)
None.
Статус выхода (Exit)
If command is specified, exec shall not return to the shell;
rather, the exit status of the process shall be the exit status
of the program implementing command, which overlaid the shell. If
command is not found, the exit status shall be 127. If command is
found, but it is not an executable utility, the exit status shall
be 126. If a redirection error occurs (see Section 2.8.1,
Consequences of Shell Errors), the shell shall exit with a value
in the range 1-125. Otherwise, exec shall return a zero exit
status.
Последствия ошибок (Consequences of errors)
Default.
The following sections are informative.
Использование в приложениях (Application usage)
None.
Примеры (Examples)
Open readfile as file descriptor 3 for reading:
exec 3< readfile
Open writefile as file descriptor 4 for writing:
exec 4> writefile
Make file descriptor 5 a copy of file descriptor 0:
exec 5<&0
Close file descriptor 3:
exec 3<&-
Cat the file maggie by replacing the current shell with the cat
utility:
exec cat maggie
Обоснование (Rationale)
Most historical implementations were not conformant in that:
foo=bar exec cmd
did not pass foo to cmd.
Будущие направления (Future directions)
None.
Смотри также (See also)
Section 2.14, Special Built-In Utilities
