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On a Linux box I want to check if a specific socket file exists. I know the socket files exists, but my checks in bash don't show that to me:
$ ls -l /var/run/supervisor.sock
srwxrw-rw- 1 root root 0 Jun 3 13:30 /var/run/supervisor.sock # <== THE FILE EXISTS!!
$ if [ ! -f /var/run/supervisor.sock ]; then echo 'file does not exist!'; fi
file does not exist!
Why oh why can't bash see that the file exists?
318
In order to check if a file does not exist using Bash, you have to use the “!” symbol followed by the “-f” option and the file that you want to check. Similarly, you can use shorter forms if you want to quickly check if a file does not exist directly in your terminal.
Checking If a Directory Exists In a Bash Shell Script-h "/path/to/dir" ] && echo "Directory /path/to/dir exists." || echo "Error: Directory /path/to/dir exists but point to $(readlink -f /path/to/dir)." The cmd2 is executed if, and only if, cmd1 returns a non-zero exit status.
Many times when writing Shell scripts, you may find yourself in a situation where you need to perform an action based on whether a file exists or not. In Bash, you can use the test command to check whether a file exists and determine the type of the file.
http://www.tldp.org/LDP/abs/html/fto.html
Use -S to test if its a socket. -f is for regular files.
See man 1 test:
-e FILE
FILE exists
-f FILE
FILE exists and is a regular file
...
...
-S FILE
FILE exists and is a socket
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