---
name: "exec"
section: "1p"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/exec/1p"
---

# exec(1p)

execute commands and open, close, or copy file descriptors

## 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.

## 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 *argument*s, 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 *argument*s 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.

## SEE ALSO

*Section 2.14*, *Special Built-In Utilities*

## COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting\_bugs.html .