cap_get_fd - Linux


The cap_get_fd() command is used to retrieve the capabilities associated with a file descriptor. It provides access to capabilities that are specific to the open file referenced by the descriptor, allowing for fine-grained control over resource access and security policies.




  • CAPABILITY (optional): One or more capability names to retrieve. If not specified, all capabilities will be retrieved.
  • CAP_FD (required): File descriptor of the file to retrieve capabilities for.


Getting All Capabilities for a File

# Get all capabilities for the /bin/bash file
cap_get_fd /bin/bash

Getting Specific Capabilities for a File

# Get the 'CAP_SETGID' and 'CAP_SETUID' capabilities for /tmp/foo
cap_get_fd CAP_SETGID,CAP_SETUID CAP_FD=/tmp/foo

Common Issues

  • Permission Denied: If the CAP_FD file descriptor does not have proper permissions, the command may fail. Ensure the caller has the required permissions to access the file.
  • Invalid CAPABILITY: If a specified capability name is invalid or not supported by the system, the command may fail with an error. Ensure the specified capabilities are valid.


cap_get_fd() can be integrated with other tools and commands to manage capabilities in various scenarios:

# Example using the `awk` command
ls -l | awk '{print cap_get_fd(CAP_CHOWN,CAP_FD=$1)}'

Related Commands

  • cap_set_fd()
  • lscap()
  • setcap()