I wrote configuration of fish shell like this:
# One or more argument(s) will be given
function run
set -l src $argv[1]
set -l var
switch "$src"
case *
set var "$src"
end
echo $var
end
I expected the first argument is printed in any case if one or more argument is given. However, $var becomes $argv[1] if file with the same name as $argv[1] exists, otherwise it becomes empty string.
Could someone tell me why?
The * in case * is interpreted as a glob. Quote it if you do not want that.
Faho already answered your question but I wanted to point out that your approach is more complicated than necessary. If you just want to print the first argument if one or more were provided do this:
set -q argv[1]
and echo $argv[1]
The first statement checks if argv has at least one value. The second echoes it if the previous statement returned success (i.e., $status set to zero).
Related
Ultimate Goal
Essentially I have a while loop going through each command-line argument passed to the script, but want to set default behaviour if no arguments are passed.
Current solution idea
My plan for this is to test if there are any arguments prior to this while loop and if there aren't any, simply add the default arguments (flags in this case) to the argument array and let the script execute from there as normal.
Problem I'm having
Where I'm tripping up a little here is figuring out the syntax to add these default arguments to the arguments array itself (I can get values from it no problem).
This is what I have so far:
if test $# -eq 0
then
# ADD --default TO ARGUMENTS ARRAY HERE
fi
while test $# -gt 0
do
case "$1" in
--opt1) DO STUFF
;;
--opt2) DO MORE / OTHER STUFF
;;
--default) DO DEFAULT STUFF
;;
esac
shift
done
Following and altering examples using user-defined arrays I have tried:
if test $# -eq 0
then
$+=('--default')
fi
But just get the syntax error
syntax error near unexpected token `'--default''
sh does not have arrays other than the built-in command-line argument list, and thus no += operator for arrays.
You also seem to be missing a character; what you wrote evaluates to assigning (default) to the value of the variable $+ but this variable is not valid (though because there are no arrays, the parentheses cause an error already).
The shell allows you to use set to manipulate the built-in argument list.
if test $# -eq 0
then
set -- --default
fi
The condition requires the array to be empty, so we simply populate it with the single element you provided; in the general case, you could add stuff to the end with
set -- "$#" --default
or correspondingly to the beginning by putting something before "$#" (which of course contains the previous value of the argument list).
I want to manipulate $argv and pass it on to another fish function. It is simple enough to trim it as follows:
switch $value
case a
set argv $argv[2..-1]
case b
set argv $argv[3..-1]
end
call_function $argv
But how can I set it to an empty list?
I don't want to set --erase argv because I do actually want to access the variable.
I tried set argv $argv[] but then count $argv returns 1. (And I may rely on count later -- unless there is a better way to test for emptiness?)
set argv
You don't actually need $argv to get to an empty list at all - the empty list is just the absence of arguments.
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 $status
do a command
end
To do a command when the previous command returned a non-success. How do I do that?
See http://fishshell.com/docs/current/commands.html#if and http://fishshell.com/docs/current/tutorial.html#tut_conditionals.
Fish's if structure looks like this:
if COMMAND
# do something if it succeeded
else
# do something if it failed ($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
The shortest short form would be
the_previous_command; or do_a_command
# ..................^^^^^
Assuming you get your $status from "the_previous_command"
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.
I've been searching all over the place and since I'm taking my first steps in PERL this might be one of he dumbest questions but here it goes.
So I'm creating a script to manage my windows and later bind it to keyboard shortcuts, so I I'm trying to run a command and passing some variables:
my $command = `wmctrl -r :ACTIVE: -e 0,0,0,$monitors->{1}->{'width'}/2,$monitors->{1}->{'height'}`;
But I get an error saying I'm not passing the right parameters to the command, but if I do this, everything works great:
my $test = $monitors->{1}->{'width'}/2;
my $command = `wmctrl -r :ACTIVE: -e 0,0,0,$test,$monitors->{1}->{'height'}`;
So do I really have to do this? assign it first to a variable and then pass it, or there's a more elegant way of doing it?
The backticks operator (or the qx{}) accepts A string which is (possibly) interpolated. So accepts string and not expression like $var/2.
Thats mean than the $variables ($var->{1}->{some} too) are expanded but not the arithmetic expressions.
Therefore your 2 step variant works, but not the first.
If you want evaluate an expression inside the string you can use the next:
my $ans=42;
print "The #{[ $ans/2 ]} is only the half of answer\n";
prints
The 21 is only the half of answer
but it is not very readable, so better and elegant is what you're already doing - calculate the command argument in andvace, and to the qx{} or backticks only pass the calculated $variables.
This question is based on this thread.
The code
function man()
{
man "$1" > /tmp/manual; less /tmp/manual
}
Problem: if I use even one option, the command does not know where is the wanted-manual
For instance,
man -k find
gives me an error, since the reference is wrong. The command reads -k as the manual.
My attempt to solve the problem in pseudo-code
if no parameters
run the initial code
if one parameter
run: man "$2"
...
In other words, we need to add an option-check to the beginning such that
Pseudo-code
man $optional-option(s) "$n" > /tmp/manual; less /tmp/manual
where $n
n=1 if zero options
n=2 if 1 option
n=3 if 2 options
....
How can you make such an "option-check" that you can alter the value of $n?
Developed Problem: to make two if loops for the situations from n=1 to n=2
How about passing all the arguments
function man()
{
man $# > /tmp/manual; less /tmp/manual
}
What is the bug in less which you mention in the title?
First, you can pass all of your function's arguments to man by using $* or $#. You can read man sh for the precise details on the difference between the two; short story is to almost always use "$#" with double quotes.
Second, the temporary file is unnecessary. You could make this a little cleaner by piping the output of man directly to less:
function man() {
man "$#" | less
}
By the way, if you're just trying to use a different pager (man uses more and you want the fancier less) there's a commonly recognized PAGER environment variable that you can set to override the default pager. You could add this to your ~/.bashrc for instance to tell all programs to use less when displaying multiple screens of output:
export PAGER=less
To answer your precise question, you can check the number of arguments with $#:
if [ $# -eq 0 ]; then
: # No arguments
elif [ $# -eq 1 ]; then
: # One argument
# etc.
You might also find the shift command helpful. It renames $2 to $1, $3 to $2, and so on. It is often used in a loop to process command-line arguments one by one:
while [ $# -gt 1 ]; do
echo "Next argument is: $1"
shift
done
echo "Last argument is: $1"