fexecve - Linux

Overview

fexecve is a Linux utility that executes a program in a separate process while inheriting the file descriptors of the parent process. It is primarily used to execute programs that communicate with the parent process through file descriptors, such as pipes, sockets, or terminals.

Syntax

fexecve [-a] [-e env-file] [-f file-descriptor] program [arguments...]

Options/Flags

  • -a: Append the environment variables from env-file to the existing environment.
  • -e env-file: Read environment variables from env-file and add them to the environment.
  • -f file-descriptor: Specify the file descriptor to use for program input. Defaults to standard input (0).

Examples

Simple execution: Execute program using the parent process’s file descriptors.

fexecve program arg1 arg2

Pass environment variables: Execute program with environment variables defined in env-file.

fexecve -e env-file program arg1 arg2

Specify input file descriptor: Execute program using file descriptor 3 for input.

fexecve -f 3 program arg1 arg2

Execute a script: Execute the script test.sh while inheriting the parent process’s file descriptors.

fexecve test.sh

Common Issues

  • Permission denied: Ensure that the specified program has execute permissions.
  • File descriptor not available: Verify that the specified file descriptor is valid.
  • Stale file descriptors: If the parent process closes a file descriptor before the child process uses it, fexecve will fail.

Integration

fexecve can be integrated with other commands to perform advanced tasks:

  • Pipe output from a program using pipe:
program | fexecve child-program args...
  • Redirect child process output to a file using >:
fexecve program args... > output.txt

Related Commands

  • execve: Similar to fexecve but doesn’t inherit file descriptors.
  • pipe: Creates a pipe for communication between processes.
  • socketpair: Creates a pair of connected sockets.