# Argument parser for bash scripts v1.6

## Usage

```shell
# 1. add these lines after shebang:

__RAW_ARGS__=("$@")
source args.sh

# 2. read arguments as flags:

arg a 1 flag_a
echo "Flag -a has value '$flag_a'"
echo "Flag -a has value '$(arg a 1)'"

arg b 1 flag_b
echo "Flag -b has value '$flag_b'"
echo "Flag -b has value '$(arg b 1)'"

arg c 1 flag_c
echo "Flag -c has value '$flag_c'"
echo "Flag -c has value '$(arg c 1)'"

arg d 1 flag_d
echo "Flag -d has value '$flag_d'"
echo "Flag -d has value '$(arg d 1)'"

argl flag1 1 flag_1
echo "Flag --flag1 has value '$flag_1'"
echo "Flag --flag1 has value '$(argl flag1 1)'"

argl flag2 1 flag_2
echo "Flag --flag2 has value '$flag_2'"
echo "Flag --flag2 has value '$(argl flag2 1)'"

# 3. and/or read arguments' values:

arg a 0 arg_a
echo "Arg -a has value '$arg_a'"
echo "Arg -a has value '$(arg a 0)'"

arg b 0 arg_b
echo "Arg -b has value '$arg_b'"
echo "Arg -b has value '$(arg b 0)'"

argl arg1 0 arg_1
echo "Arg --arg1 has value '$arg_1'"
echo "Arg --arg1 has value '$(argl arg1 0)'"

argl arg2 0 arg_2
echo "Arg --arg2 has value '$arg_2'"
echo "Arg --arg2 has value '$(argl arg2 0)'"
```

## How it works

1. Short arguments can be specified contiguously or separately
   and their order does not matter, but before each of them
   (or the first of them) one leading dash must be specified.

   > Valid combinations: `-a -b -c`, `-cba`, `-b -azc "value of z"`

2. Short arguments can have values and if are - value must go
   next to argument itself.
   
   > Valid combinations: `-ab avalue`, `-ba avalue`, `-a avalue -b`
   
3. Long arguments cannot be combined like short ones and each
   of them must be specified separately with two leading dashes.
   
   > Valid combinations: `--foo --bar`, `--bar --foo`
   
4. Long arguments can have a value which must be specified after `=`.
   
   > Valid combinations: `--foo value --bar`, `--bar --foo=value`
   
5. If arg value may contain space then value must be "double-quoted".

6. You can use arg() or argl() to check presence of any arg, no matter
   if it has value or not.

More info:
* 🇷🇺 [axenov.dev/bash-args](https://axenov.dev/bash-args/)
* 🇺🇸 [axenov.dev/en/bash-processing-arguments-in-a-script-when-called-from-the-shell/](https://axenov.dev/en/bash-processing-arguments-in-a-script-when-called-from-the-shell)

Tested in Ubuntu 20.04.2 LTS in:

```
bash 5.0.17(1)-release (x86_64-pc-linux-gnu) and later
zsh 5.8 (x86_64-ubuntu-linux-gnu) and later
```

## Version history

```
v1.0 - initial
v1.1 - arg(): improved skipping uninteresting args
     - arg(): check next arg to be valid value
v1.2 - removed all 'return' statements
     - arg(): error message corrected
     - new examples
v1.3 - argl(): improved flag check
     - some text corrections
v1.4 - new function argn()
     - some text corrections
v1.5 - arg(), grep_match(): fixed searching for -e argument
     - grep_match(): redirect output into /dev/null
v1.6 - removed useless argn()
     - arg() and argl() refactored and now support values with whitespaces
```