---
name: "rexec"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/rexec/3"
---

# rexec(3)

return stream to a remote command

## NAME

**rexec** – return stream to a remote command

## LIBRARY

library “libcompat”

## SYNOPSIS

*int*\

**rexec**(*char \*\*ahost*, *int inport*, *char \*user*, *char \*passwd*, *char \*cmd*, *int \*fd2p*);

## DESCRIPTION

This interface is obsoleted by [rcmd(3)](/rcmd/3.md).

The **rexec**() function looks up the host *\*ahost* using [gethostbyname(3)](/gethostbyname/3.md), returning -1 if the host does not exist. Otherwise *\*ahost* is set to the standard name of the host. If a username and password are both specified, then these are used to authenticate to the foreign host; otherwise the environment and then the user's *.netrc* file in his home directory are searched for appropriate information. If all this fails, the user is prompted for the information.

The port *inport* specifies which well-known DARPA Internet port to use for the connection; the call **getservbyname**(*exec*, *tcp*) (see [getservent(3)](/getservent/3.md)) will return a pointer to a structure, which contains the necessary port. The protocol for connection is described in detail in [rexecd(8)](/rexecd/8.md).

If the connection succeeds, a socket in the Internet domain of type SOCK\_STREAM is returned to the caller, and given to the remote command as stdin and stdout. If *fd2p* is non-zero, then an auxiliary channel to a control process will be setup, and a descriptor for it will be placed in *\*fd2p*. The control process will return diagnostic output from the command (unit 2) on this channel, and will also accept bytes on this channel as being UNIX signal numbers, to be forwarded to the process group of the command. The diagnostic information returned does not include remote authorization failure, as the secondary connection is set up after authorization has been verified. If *fd2p* is 0, then the stderr (unit 2 of the remote command) will be made the same as the stdout and no provision is made for sending arbitrary signals to the remote process, although you may be able to get its attention by using out-of-band data.

## SEE ALSO

[rcmd(3)](/rcmd/3.md), [rexecd(8)](/rexecd/8.md)

## HISTORY

The **rexec**() function appeared in 4.2BSD.

## BUGS

The **rexec**() function sends the unencrypted password across the network.

The underlying service is considered a big security hole and therefore not enabled on many sites, see [rexecd(8)](/rexecd/8.md) for explanations.