Bash file existence checking missing ] [closed]

Question

I am attempting a simple file existence check in my bash script:

FILE_TO_CHECK=/home/username/path/to/file

if [ ! -f $FILE_TO_CHECK]; #line 9 in actual script
then
    echo File not found.
fi

Seems simple enough to me, but I'm getting the following error and I don't know why:

/path/to/script: line 9: [: missing `]'

I'm not exactly a bash expert, but I was pretty sure a backtick is not necessary in this context. What gives?

Answer 1

Missing space before the closing ].

You have to understand that [ is a command and everything following it, until the ;, are its arguments. Command [ expects its last argument to be ]. But if you omit the space, then ] becomes the last character of the previous argument.

It might seem that [ ] is part of the if syntax. It's not the case. if has to be followed by any command, and if evaluates its exit status.

if true; then foo; fi

In the above line true is a command too.

$ which true
/bin/true

true is a command with the sole purpose of always having a true (0) exit status.

Answer 2

You could also try:

if (test ! -f $FILE_TO_CHECK);

or

if !(test -f $FILE_TO_CHECK);

as [ is a shorthand for the test command.