This is the command execposix that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator
PROGRAM:
NAME
exec — execute commands and open, close, or copy file descriptors
SYNOPSIS
exec [command [argument...]]
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.
OPTIONS
None.
OPERANDS
See the DESCRIPTION.
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
None.
ASYNCHRONOUS EVENTS
Default.
STDOUT
Not used.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
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.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
None.
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
RATIONALE
Most historical implementations were not conformant in that:
foo=bar exec cmd
did not pass foo to cmd.
FUTURE DIRECTIONS
None.
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