BASH + Best method of converting fields to variables

[Steven W. Orr]

On Friday, Jul 16th 2004 at 17:23 -0700, quoth Ow Mun Heng:

=>Guys,
=>
=>	Writing a batch_create_new_user script.
=>input is a file with this format
=>
=>Username:Full Name:Default Group:Default Shell:Home Directory:Password
=> 
=>and the using those fields ($1 $2 $3 etc) and passing then to the useradd program
=>
=>I'm having some trouble getting bash to get the positional fields into variables which I
=>can then plug into useradd
=>
=>eg:
=>pseudo code
=>for each line in input file
=>  do
=>	username=$1
=>	name=$2
=>	useradd -c "$2" $1
=>  done
=>
=>I ended up using awk, which works but seems complicated
=>
=>	eval `awk -F ':' \
=>        '{printf ("useradd -c \"%s\" ",$2)}; \
=>        length($3)>0 {printf ("-g %s ",$3)}; \
=>        length($4)>0 {printf ("-s %s ",$4)}; \
=>        length($5)>0 {printf ("-d %s ",$5)}; \
=>        {printf ("%s\n;",$1)};' $1`
=>
=>Can it be done using bash itself? (without calling awk)
=>Actually I was hoping I can get awk to get the fields for the variables
=>
=>psuedo code
=>username = awk -F: {'print $1}'
=>name = awk -F: {'print $2}'
=>
=>Any takers??
=>
=>BTW, what's the best way to check the number of fields in the input file?
=>I was thinkning of counting how many ":" there are in each line. But can't
=>figure out how to actually _do_ it.

Easy peasy japanesy.

#! /bin/bash
typeset IFS=:

while read f1 f2 f3 f4 f5
do
    useradd -c f2 -g $f3 -s $f4 -d $f5 $f1
done < input_file


But if all the fields (except for the first one are optional) then
just do dis:

#! /bin/bash
typeset IFS=:

while read f1 f2 f3 f4 f5
do
    cmd=useradd
    [[ -n "$f2" ]] && cmd="$cmd -c $f2"
    [[ -n "$f3" ]] && cmd="$cmd -g $f3"
    [[ -n "$f4" ]] && cmd="$cmd -s $f4"
    [[ -n "$f5" ]] && cmd="$cmd -d $f5"
    cmd="$cmd $f1"
    eval "$cmd"
done < input_file

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