What does -f mean in bash

Question

I was looking at how to use runit to run gunicorn. I was looking at the bash file and I don't know what -f $PID does in

#!/bin/sh

GUNICORN=/usr/local/bin/gunicorn
ROOT=/path/to/project
PID=/var/run/gunicorn.pid

APP=main:application

if [ -f $PID ]; then rm $PID; fi

cd $ROOT
exec $GUNICORN -c $ROOT/gunicorn.conf.py --pid=$PID $APP

Google is useless in this case because searching for flags is useless

Answer 1

Google is useless in this case because searching for flags is useless

Fortunately, the Bash Reference Manual is available online, at http://www.gnu.org/software/bash/manual/bashref.html. It's the first hit when you Google for "Bash manual". §6.4 "Bash Conditional Expressions" says:

-f file

True if file exists and is a regular file.

Answer 2

[ -f "$var" ] 

Checks if $var is an existing file (regular file). Symbolic link passes this test too.

Answer 3

-f checks if the file exists and is a regular file.

Answer 4

-f - file is a regular file (not a directory or device file)

Check this out for all file test operators: http://tldp.org/LDP/abs/html/fto.html

Answer 5

The [ is the same as the command test which allows you to test certain things. Try help test to find out what the flags are. Things to be careful with are spaces - the [ needs a space after it.