Succinctly split BASH command string into arguments and flags

Question

My BASH command string ($@) looks like this: cmd -arg1 foo bar --flag1 --flag2

Flags come after args, and I don't have any awkward gotchas in the args (I am building an internal tool for my own use).

How can I extract -arg1 foo -arg2 bar into $args and --flag1 --flag2 into $flags?

P i · Accepted Answer · 2021-01-20 20:28:02Z

0

The following works, although I suspect it is not optimal:


> echo $x
cmd -arg1 foo bar --flag1 --flag2

> flags="--${x#*--}"

> echo $flags
--flag1 --flag2

> before_flags=${x%%"$flags"}

> echo $before_flags
cmd -arg1 foo bar

> set $before_flags

> echo $1
cmd

> echo $2
-arg1

> echo $3
foo

> echo $4
bar

Ref: https://mywiki.wooledge.org/BashFAQ/100 -- How do I do string manipulations in bash?
Ref: https://mywiki.wooledge.org/BashFAQ/035 -- How can I handle command-line options and arguments in my script easily?

answered Jan 20, 2021 at 20:28

P i

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2 Comments

Gordon Davisson Over a year ago

It looks like you're treating the argument list as a single space-delimited string, rather than a series of separate arguments (e.g. as an array). This will cause trouble if any arguments contain whitespace and/or filename wildcard characters. Also, it's more normal to have flags before regular arguments.

markp-fuso Over a year ago

this doesn't work unless you know with 100% certainty that you'll always have options and flags provided in this same exact format, eg, the proposed code (obviously) does not work for x="cmd bar --flag2 -arg1 foo --flag1"; perhaps a nonsensical example but without some idea of the possible combos that you'll have to realistically deal with ...

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