Argbash is a code generator, so what it does, it gives you code that has the ability to parse command-line arguments.
The question is — what to do with the generated code?
You have three options here, they are sorted by the estimated preference:
One file with both parsing code and script body — batteries are included!
This is a both simple and functional approach, but the argument parsing code will pollute your script.
Two files — one for the parsing code and one for the script body, both taken care of by
Argbash— separation of code, but you get things managed by
This is more suitable for people that prefer to keep things tidy, you can have the parsing code separate and included in the script at run-time. However,
Argbashcan assist you with that.
Same as the above, just without
Argbashassistance — the parsing code is decoupled from the script.
You have to take this path if your script has a non-matching square brackets problem (see Limitations). This approach is similar to the approach of
bashargument parsing libraries with one difference — here, the library is generated by
Argbash, so it may be significantly less complex than those generic libraries such as EasyOptions. This is very unlikely.
We assume that you have installed (see Installation) the
argbash script, so it is available in your terminal as a command
If it is not the case, you just have to substitute
argbash by direct invocation of
It is not advisable to write a template from scratch, since
Argbash contains a tool for that.
argbash-init can generate a good starting template for you, so you can get started within minutes.
The most efficient way of using
Argbash is probably this one (also covered in an example):
- Get an idea of what arguments your script should accept.
argbash-initwith the right arguments to get a basic template.
- Replace placeholders in the template with meaningful values.
- Expand the template with another directives (if necessary) based on argbash API.
argbashover the template.
argbash-init supports generating templates with these types of arguments:
- Single-valued positional arguments (
- Single-valued optional arguments (
- Boolean optional arguments (
Generally, you specify argument name and you add help etc. by editing the template file.
argbash-init supports wrapping of another argbash-aware scripts.
The help macro is always included.
Modes of operation¶
argbash-init allows you to select the way how the parsing code is handled (via the
If you don’t specify it, you get the case 1 from above — the parsing code is embedded in the script.
If you specify it exactly once, you get the case 2 from above — parsing code is in a separate file, but both files contain
If you specify twice, you get the case 3 from above — parsing code is in a separate file, the script includes it without any magic involved. This also means that the brackets matching limitation doesn’t apply to you.
There is also a
--mode option you can use to tune the balance between parsing features and complexity of the generated code.
default: Assume the standard
Argbashbehavior. Check the documentation out to find out what that means.
full: Maximize script features. * The long option and the corresponding value may be separated by whitespace or by the equal sign. * Variables corresponding to every positional argument is declared (.. seealso::_declare_pos).
minimal: Make the code as simple as possible, which means: * The long option and the corresponding value may be separated only by whitespace.
So, you have a template and now it is time to (re)generate a shell script from it!
A template consists of multiple parts that are treated differently during the
Depending on the value of the
--strip argument, the third and/or the first parts can be dropped.
Here are those parts of the template:
Beginning of the script up to the
--strip allis passed as argument to
argbash, this section of the file will be discarded. Otherwise, it is left intact, except:
m4sugarmacros are expanded. Typically, the only macros in this section are Argbash public API macros. They expand to their definitions as part of their expansion, so it looks like that nothing happened.
- One level of square brackets is removed. This is the consequence of the previous point — if you e.g. use a regular expression with square brackets, they may either disappear or cause an error. Square brackets that are arguments to the Argbash macros calls are preserved.
Script body past
This is the generated content. Shortly after the
ARGBASH_GOline, you encounter an invocation of
m4_ignore([...]). Everything contained within the first level of the square brackets is discarded by a consecutive run of
The rest of the file.
If you run
--strip allargument, this section will be missing from the output altogether. Otherwise, the preexisting content is preserved with some noteworthy points:
- You may notice the
# [ <-- needed because of Argbashand
# ] <-- needed because of Argbashguards. The first guard has an opening square bracket, the second guard at the bottom of the file has a closing square bracket. Don’t remove them, they are necessary for
argbashto be idempotent.
- This part of the file (typically the hand-written content supplied by the user) is treated in the same way as the beginning of the file that is described in point 1. However, thanks to the opened and closed square brackets, no changes to it will be made.
- You may notice the
Parsing code and script body together¶
Assuming that you have created a template file
my-template.m4, you simply run
argbash over the script [*]:
argbash my-template.m4 -o my-script.sh
If you want to regenerate a new version of
my-script.sh after you have modified its template section, you can run
argbash my-script.sh -o my-script.sh
as the script can deal with input and output being the same file.
Separate file for parsing with assistance¶
You have two files, let’s say it is a
my-parsing.m4 file contains just the template section of
Then, you add a very small template code to
my-script.sh at the beginning:
# DEFINE_SCRIPT_DIR # INCLUDE_PARSING_CODE([my-parsing.sh]) # ARGBASH_GO # [ <-- needed because of Argbash # HERE GOES THE SCRIPT BODY # ] <-- needed because of Argbash
i.e. you add those three lines with definitions and you enclose the script in square brackets.
Finally, you just make sure that
my-parsing.m4 are next to each other and run
argbash my-script.sh -o my-script.sh
my-parsing.m4 (it would find
my-parsing.sh too) and generates new
my-script.sh that you can use right away.
my-parsing.sh are found, the more recent one is used to generate the
Separate file for parsing¶
If you want/have to take care of including the parsing code yourself, just make sure you do it in the script — for example:
source $(dirname $0)/my-parsing.sh # HERE GOES THE SCRIPT BODY
Then, you just generate
--strip user-content option:
argbash my-parsing.m4 -o my-parsing.sh --strip user-content
--strip user-content argument takes care that the output will contain the Argbash definitions lines and the generated parsing code, but the body of the script will not be included.
Argbash is able to generate more than just scripts.
You can change the output type by supplying another value to he
--type optional argument.
Next, it doesn’t make sense to keep all of the template content in the output, so you may typically want to strip all but the generated content from alternative outputs:
|Bash script parsing section||bash-script||user-content|
|POSIX script parsing section||posix-script||user-content|
|docopt help message||docopt||all|
Argbash is able to generate code that will work with POSIX shells. Due to limitations of those shells (mainly absence of arrays), the generated interface features are limited:
- All options have to have short option. Those short options are the only user-visible element of the interface.
- Mixing optional and positional arguments is not supported, all arguments that follow the first positional argument are considered positional.
- Certain arguments are not supported:
- Repeated arguments.
- Multi-valued argumetns.
Internally, Argbash uses the
getopts shell builtin to handle optional arguments parsing.
Then, checks for positional arguments are generated and applied, ditto for positional arguments processing, and the help message is generated.
As a result, the parsing section of a POSIX script is shorter.
The output will be a Bash completion script.
Notice that in this case, the completion file has to “know” the basename of the script the completion is meant for.
The basename is inferred either from the source filename, or from the destination by stripping the
.m4 suffix if applicable
The general recommendation is not to save your scripts to files without suffixes.
.sh suffixe only for files that are Bash modules.
After you generate the completion file, put it in the appropriate place (which may vary depending on your environment). In order to use it right away, simply source it.
Typically, you generate bash completion
my-script.sh from the generated script
my-script by executing
$ argbash my-script --type completion --strip all -o my-script.sh
and you move the created completion file
Docopt help message¶
Docopt is a project that provides argument-parsing libraries for various languages.
Those libraries accept a help message as an input, and that’s all they want to construct a parser.
Argbash scripts don’t come with help that conforms to the
docopt format due to its constraints, but you can still generate
docopt-compliant help for your script.
This allows you to use Argbash for projects in other languages — you can leave the parser technicalities to docopt library, which you supply with the Argbash docopt output. Then, you may use Argbash for Bash completion and other possible goodies.
Typically, you generate docopt output to the standard output from the generated script
my-script by executing
$ argbash my-script --type docopt --strip all
API changes support¶
The API of the
Argbash project may change.
This typically means that
- names, parameters or effect of macros change, or
- parsed arguments are exposed differently
in a way that is not compatible with the previous API.
In case that you regenerate a script,
argbash is able to deduce that it has been created with another version of
Argbash and warns you.
In that case, you can use a
argbash-xtoy script, where
x is the version of
Argbash your script is written for and
y is version of
Argbash you use now.
To upgrade your script from
Argbash version 1 to 2, you simply invoke:
argbash-1to2 my-script.sh -o my-script.sh
You can use the utility to convert scripts as well as
Always back your scripts up and perform diff between the output and the original after using