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implement a new implicit int option spec

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While updating the `history` function to use `argparse` I realized it is
useful to define an option that can be used in three ways. First by
using the short flag; e.g., `-n NNN`. Second by using the long flag;
e.g., `--max NNN`. Third, as an implicit int flag; e.g., `-NNN`. This
use case is now supported by a spec of the form `n#max`.
This commit is contained in:
Kurtis Rader
2017-07-16 18:27:41 -07:00
parent 06d071dd94
commit 3e226f0a5e
6 changed files with 78 additions and 10 deletions
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6
doc_src/argparse.txt
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@@ -62,11 +62,11 @@ Each option specification is a string composed of
- A short flag letter (which is mandatory). It must be an alphanumeric or "#". The "#" character is special and means that a flag of the form `-123` is valid. The short flag "#" must be followed by "-" (since the short name isn't otherwise valid since `_flag_#` is not a valid var name) and must but followed by a long flag name with no modifiers.
- A `/` if the short flag can be used by someone invoking your command else `-` if it should not be exposed as a valid short flag. If there is no long flag name these characters should be omitted.
- A `/` if the short flag can be used by someone invoking your command else `-` if it should not be exposed as a valid short flag. If there is no long flag name these characters should be omitted. You can also specify a '#' to indicate the short and long flag names can be used and the value can be specified as an implicit int; i.e., a flag of the form `-NNN`.
- A long flag name which is optional. If not present then only the short flag letter can be used.
- Nothing if the flag is a boolean that takes no argument, else
- Nothing if the flag is a boolean that takes no argument or is an implicit int flag, else
- `=` if it requires a value and only the last instance of the flag is saved, else
@@ -100,6 +100,8 @@ Some OPTION_SPEC examples:
- `#-max` means that flags matching the regex "^--?\d+$" are valid. When seen they are assigned to the variable `_flag_max`. This allows any valid positive or negative integer to be specified by prefixing it with a single "-". Many commands support this idiom. For example `head -3 /a/file` to emit only the first three lines of /a/file.
- `n#max` means that flags matching the regex "^--?\d+$" are valid. When seen they are assigned to the variables `_flag_n` and `_flag_max`. This allows any valid positive or negative integer to be specified by prefixing it with a single "-". Many commands support this idiom. For example `head -3 /a/file` to emit only the first three lines of /a/file. You can also specify the value using either flag: `-n NNN` or `--max NNN` in this example.
After parsing the arguments the `argv` var is set with local scope to any values not already consumed during flag processing. If there are not unbound values the var is set but `count $argv` will be zero.
If an error occurs during argparse processing it will exit with a non-zero status and appropriate error messages are written to stderr.