SH: two variables in for loop

marcpascual · #1 (**permalink**) 07-30-2008

Hi, say I have a simple sh script like this:

Code:

for i in a b c d
        do
                for j in 1 2 3 4
                        do
                                echo "$i $j"
                        done
        done

and the output is

Code:

 a 1
 a 2
 a 3
 a 4
 b 1
 b 2
 b 3
 b 4
 c 1
 c 2
 c 3
 c 4
 d 1
 d 2
 d 3
 d 4

how do i make its output like this?

Code:

a 1
b 2
c 3
d 4

TIA

cfajohnson · #2 (**permalink**) 07-30-2008

Don't use two loops.

Code:

n=1
for l in a b c d
do
   printf "%s %d\n" "$l" "$n"
   n=$(( $n + 1 ))
done

marcpascual · #3 (**permalink**) 07-30-2008

Thanks, I need to re-qualify my question:

what if its not a number and you can't do math on it?

e.g.
list1:
mary
eve
delilah

list2:
joseph
adam
samson

output:
mary joseph
adam eve
samson delilah

for i in `cat list1`; ... for j in `cat list2`; ... do ... print $i $j ... done

any way around this?

cfajohnson · #4 (**permalink**) 07-30-2008

Quote:

Originally Posted by marcpascual

Thanks, I need to re-qualify my question:

what if its not a number and you can't do math on it?

e.g.
list1:
mary
eve
delilah

list2:
joseph
adam
samson

output:
mary joseph
adam eve
samson delilah

for i in `cat list1`; ... for j in `cat list2`; ... do ... print $i $j ... done

any way around this?

Code:

set -f
IFS='
'
set -- $( cat list2 )
for i in `cat list1`
do
  printf "%s %s\n" "$i" "$1"
  shift
done

marcpascual · #5 (**permalink**) 07-30-2008

amazing, thank you!

danmero · #6 (**permalink**) 07-30-2008

Quote:

Originally Posted by cfajohnson

Code:

set -f
IFS='
'
set -- $( cat list2 )
for i in `cat list1`
do
  printf "%s %s\n" "$i" "$1"
  shift
done

KISS principle states that design simplicity should be a key goal and unnecessary complexity avoided.

Code:

paste -d ' ' list1 list2

Exolon · #7 (**permalink**) 08-01-2008

Quote:

Originally Posted by marcpascual

how do i make its output like this?

Code:

a 1
b 2
c 3
d 4

It seems you can't have multiple "x in y" terms in a for loop, so the next best thing is probably to rewrite the loop as an index iterator:

Code:

is=(a b c d)
js=(1 2 3 4)

for ((i = 0; i < 4; i++)) 
	do echo ${is[i]} ${js[i]}
done

It's not as nice, but still relatively easy to read, especially if you define your lists together.

More UNIX and Linux Forum Topics You Might Find Helpful
Thread	Thread Starter	Forum	Replies	Last Post
foreach loop + 2 variables	JamesGoh	Shell Programming and Scripting	3	06-04-2008 03:36 AM
using variables outside a while loop	Tornado	Shell Programming and Scripting	2	02-09-2007 01:26 AM
adding variables for, for loop	jazz	High Level Programming	3	03-13-2006 04:23 AM
Writing to variables within a loop	Sniper Pixie	UNIX for Dummies Questions & Answers	0	03-02-2006 09:11 AM
for loop with multiple variables ?	fosterian	Shell Programming and Scripting	3	03-01-2004 05:15 AM

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes	Rate This Thread
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode	Rate This Thread: