Linux bash, getting getopt default parameters

Question

I'm trying to write a moderately difficult bash program, but somehow I cannot parse command line parameters and set default parameters with getopt.

Getopt is somehow ignoring optional parameters, setting them after the --, which denotes end of parameters.

Simple test, where l(list) is required:

getopt -s bash -o l: -l list: -- -l test

Produces:

-l 'test' --

If I were to define l(list) as optional, then output is:

getopt -s bash -o l:: -l list:: -- -l test

-l '' -- 'test'

I used this example as a base, but as of my testing, even this script does not work as intended(setting arga value to something produces always default value).

OS: Linux, getopt -V=getopt from util-linux 2.27

Any help appreciated :)

IIRC getopts will only work with short options, not long ones. The code in that tutorial is doing its own parsing to iterate through options. There are almost certainly a lot of questions/answers/examples on SO (and the rest of the web) about this. — zxq9
– zxq9, Commented Oct 15, 2015 at 14:13

glenn jackman · Accepted Answer · 2015-10-15 14:39:09Z

4

Check the man page:

A simple short option is a '-' followed by a short option character. If the option has a required argument, it may be written directly after the option character or as the next parameter (i.e. separated by whitespace on the command line). If the option has an optional argument, it must be written directly after the option character if present.

So you want

$ getopt -s bash -o l:: -l list:: -- -ltest
 -l 'test' --

Similarly, for optional long args, you must provide the argument in a specific way:

required

$ getopt -s bash -o l: -l list: -- --list foo
 --list 'foo' --
$ getopt -s bash -o l: -l list: -- --list=foo
 --list 'foo' --

optional

$ getopt -s bash -o l:: -l list:: -- --list foo
 --list '' -- 'foo'
$ getopt -s bash -o l:: -l list:: -- --list=foo
 --list 'foo' --

answered Oct 15, 2015 at 14:39

glenn jackman

249k42 gold badges233 silver badges362 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

user1190411 Over a year ago

Thank you for pointing out the relevant part in manual. I read the manual, but seems I skimmed over it, was too long. getopt seems a little inconsistent in style between mandatory arguments and optional arguments. Seems I had Idée fixe, that all programs in linuxland supporting long parameters use program --param <arg|undefined>

zxq9 Over a year ago

Thanks for setting me straight. I didn't even notice the difference -- I don't do enough bash these days to remember the details without typing man foo constantly.

Collectives™ on Stack Overflow

Linux bash, getting getopt default parameters

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related