CODEWITHSUNDEEP
fish
pitosalas
pitosalas

Reputation: 10862

Fish Shell: Conditional execution based on $status?

In the fish shell the syntax for conditionals is hard to find. Does anyone have a link to an explanation of how to write an if, with ands and ors?

In particular I would like to write

if not $status
  do a command
end

To do a command when the previous command returned a non-success. How do I do that?

Upvotes: 4

Views: 3473

Answers (3)

glenn jackman
glenn jackman

Reputation: 246774

The shortest short form would be

the_previous_command; or do_a_command
# ..................^^^^^

Assuming you get your $status from "the_previous_command"

Upvotes: 2

faho
faho

Reputation: 15924

See http://fishshell.com/docs/current/commands.html#if and http://fishshell.com/docs/current/tutorial.html#tut_conditionals.

Fish's if structure looks like this:

if COMMAND
   # do something if it succeeded
else
   # do something if it failed ($status != 0)
end

Then there are also the not, and and or commands, that you can use like

if not COMMAND1; or COMMAND2
    # and so on

If you really want to test a variable (e.g. $status), you need to use test as the command, like

if test $status -eq 0

Do keep in mind that $status changes after every command, so if you need to use the status of an earlier command (common in prompts) you need to do what Joachim Pileborg said, save it to another variable.

Also, test has some issues with quotes (because it's one of the few parts of fish to adhere to POSIX) - if in test $foo -eq 0 $foo is undefined, test will error out, and if it is undefined in test -n $foo, the test will be true (because POSIX demands that test with one argument be true).

As a sidenote, in fish versions before 2.3.0, you need to add begin and end around a condition with and or or because it was interpreted weirdly.

So you'd have to do

if begin COMMAND; or COMMAND2; end # do something for status = 0

Upvotes: 8

Some programmer dude
Some programmer dude

Reputation: 409166

I use the status variable to display it on the prompt if it's non-zero. For that I use the following function:

function __pileon_status_prompt
        set -l __status $status
        if test $__status != 0
                printf '[%s%s%s]' (set_color red) $__status (set_color normal)
        end
end

As you can see I set a local variable to the value of $status and the check that variable in the condition.

Upvotes: 1

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