How to disable file descriptors in Bash scripts

In the Bash script, how does one close the file descriptor and encounter A problem when writing A Bash script tonight? This script is used to start A program B, which is called by another program, the result shows that many file descriptors opened by process A (such as Socket) exist in the newly started process B ). So I decided to close them in the script, because for the sake of simplicity, I used system () in program A to start the script. The script for disabling file descriptors is added as follows: www.2cto.com #! /Bin/sh cd $ (dirname "$0") | exit 1 exec 3> &-exec 4> &-. /rbtunnel "$ @" & # sleep 1 the key point here is to close the code of the file Description: exec fd> &-or: exec fd <&-where fd is the number of the file descriptor, and the file descriptor can be viewed in Linux Through lsof-c rbtunnel.