Diff for "BashFAQ/025"

Differences between revisions 19 and 20

I'm Willy and I live with my husband and our 3 children in Argenteuil, in the ILE-DE-FRANCE south area. My hobbies are Paintball, Jewelry making and Element collecting.

Here is my web-site; bubblegum casting

-  ⇤ ← Revision 19 as of 2013-12-30 00:15:31 → 
  Size: 1935
  Editor: GreyCat
  Comment: spam
+   ← Revision 20 as of 2014-01-10 02:39:39 → ⇥
  Size: 263
  Editor: AishaDorm
  Comment:
-Deletions are marked like this.
+Additions are marked like this.
 Line 1:
-<<Anchor(faq25)>>
== How can I access positional parameters after $9? ==
Use {{{${10} }}}instead of {{{$10}}}. This works for [[BASH]] and KornShell, but not for older BourneShell implementations. Another way to access arbitrary positional parameters after $9 is to use {{{for}}}, e.g. to get the last parameter:

{{{
    # Bourne
    for last
    do
        : # nothing
    done

    echo "last argument is: $last"
}}}

To get an argument by number, we can use a counter:

{{{
    # Bourne
    n=12        # This is the number of the argument we are interested in
    i=1
    for arg
    do
        if test $i -eq $n
        then
            argn=$arg
            break
        fi
        i=`expr $i + 1`
    done
    echo "argument number $n is: $argn"
}}}

This has the advantage of not "consuming" the arguments. If this is no problem, the {{{shift}}} command discards the first positional arguments:

{{{
    shift 11
    echo "the 12th argument is: $1"
}}}

In addition, bash and ksh93 treat the set of positional parameters as an [[BashFAQ/005|array]], and you may use [[BashFAQ/073|parameter expansion]] syntax to address those elements in a variety of ways:

{{{
    # Bash, ksh93
    for x in "${@:(-2)}"    # iterate over the last 2 parameters
    for y in "${@:2}"       # iterate over all parameters starting at $2
                            # which may be useful if we don't want to shift
}}}

Although direct access to any positional argument is possible this way, it's seldom needed. The common alternative is to use {{{getopts}}} to process options (e.g. "-l", or "-o filename"), and then use either {{{for}}} or {{{while}}} to process all the remaining arguments in turn. An explanation of how to process command line arguments is available in [[BashFAQ/035|FAQ #35]], and another is found at http://www.shelldorado.com/goodcoding/cmdargs.html

----
CategoryShell
+I'm Willy and I live with my husband and our 3 children in Argenteuil, in the ILE-DE-FRANCE south area. My hobbies are Paintball, Jewelry making and Element collecting.<<BR>>
<<BR>>
Here is my web-site; [[http://bubblegumcasting.jimdo.com/|bubblegum casting]]