Command line arguments in Bash [duplicate]

Question

This question already has answers here:

How do I parse command line arguments in Bash? (43 answers)

Closed 9 years ago.

I want to write a bash script which takes different arguments. It should be used like normal linux console programs:

my_bash_script -p 2 -l 5 -t 20

So the value 2 should be saved in a variable called pages and the parameter l should be saved in a variable called length and the value 20 should be saved in a variable time.

What is the best way to do this?

• Joe: A variable in what? Parameters are related to the program you're runnning, not bash in this case. Does 'myProgramm' take parameters?
• Pascal: I want to write a program in bash which does this.
• chepner: Note that unless you call the script using '.' (. myProgram -p2 -l 5 -t 20), the variables you set will only exist in myProgram, not the shell from which you call it.
• Captain Lepton: It really seems to me that his intention is that myProgramm is a bash script. In which case getopts is correct. To avoid this confusion maybe myProgramm should be called my_bash_script. Hey what the heck I'll edit it

Answer 1

Use the getopts builtin:
here's a tutorial

pages= length= time=
while getopts p:l:t: opt; do
 case $opt in
 p)
 pages=$OPTARG
 ;;
 l)
 length=$OPTARG
 ;;
 t)
 time=$OPTARG
 ;;
 esac
done
shift $((OPTIND - 1))

shift $((OPTIND - 1)) shifts the command line parameters so that you can access possible arguments to your script, i.e. 1,ドル 2,ドル ...

• Federico: mywiki.wooledge.org/BashFAQ/035 "getopt cannot handle empty arguments strings, or arguments with embedded whitespace. Please forget that it ever existed."
• tzelleke: @Federico your confusing getopt and getopts... you should read your citation carefully (and please retract the down vote). You can also read here

Answer 2

Something along the lines of

pages=
length=
time=
while test $# -gt 0
do
 case 1ドル in
 -p)
 pages=2ドル
 shift
 ;;
 -l)
 length=2ドル
 shift
 ;;
 -t)
 time=2ドル
 shift
 ;;
 *)
 echo >&2 "Invalid argument: 1ドル"
 ;;
 esac
 shift
done

• Steven Mackenzie: -1, far better to use getopts
• Charles Duffy: @StevenMackenzie, ...I'm not sure I can agree. If you look at BashFAQ #35, the manual-parsing example (of which this is further simplification) does rather a number of things that getopts simply can't. Following the practice is thus more flexible.
• Charles Duffy: @StevenMackenzie, ...we're also in a world where folks have been spoiled by GNUisms such as being able to mix optional and positional arguments (barring the use of -- to explicitly signal end of the former and beginning of the latter alone). It's easy to do something like args+=( "1ドル" ) in a default case with a parser of this kind; with getopts, the cutoff at OPTIND is hard-and-fast.
• Brian Agnew: Bash FAQ 35 (as above) tells me everything I need to know