Question

I am writing a post-update script for a git repository and am having a bit of trouble.

For whatever reason the if statement is throwing an error:

hooks/post-update: line 5: [master: command not found

I simply want to check and see if the pushed branch is equal to “master”. I am guessing there is something wrong with my syntax, this is my first sh script, but I’ve tried several variations with no luck.

Thanks for any help,

#!/bin/sh

BRANCH=$(git rev-parse --symbolic --abbrev-ref $1)

if ["$BRANCH" = "master"]
then
    cd $HOME/domain.com || exit
else
    cd $HOME/dev.domain.com || exit
fi

unset GIT_DIR
git pull hub $BRANCH
git checkout $BRANCH
exec git-update-server-info

Answer 1

The square brackets must be separate tokens! You see, it tries to look like nice syntax, but the fact is, that there is a (built-in in most shells) command [. So the syntax should be:

if [ "$BRANCH" = "master" ]
    ^                    ^
    +--------------------+-- There have to be spaces here!

Without the first space the command becomes [master and such command does not exist — the command is [. Without the second space, the right argument will be master] and won’t match (and than [ will fail with “missing ] argument” error.

---

Detailed description:

The shell if syntax tries to be as simple as possible. It really is

if command than command [else command] fi

where each command has to be terminated either by semicolon or end of line. So you can write things like

if grep -q foo somewhere
then
    whatever
fi

Now in many cases you need to do things like compare strings, compare numbers, test whether file exists, test whether one file is newer than another etc. For this there is a standard command test (which is built-in in most shells, but external version always exists). It allows things like

test "$foo" == "bar"
test -n "$this_variable_must_be_nonempty"
test -f "$this_file_should_exist"

This is what you use in if. For sake of nicer syntax, this command has alias [ which accepts exactly the same arguments, except it requires ] as it’s last argument so the condition looks pretty. This is also built-in in most shells, but usually exists as symlink to test too. So don’t be fooled by what looks like special syntax; it is simple program invocation.