how can we use multiple variables in single for loop in shell script?

Question

I am implementing as below code using for loop but wrong output coming after running the script.

for i in `awk -F"|" '{print $1}' $INPUTFILE`, j in `awk -F"|" '{print $2}' $INPUTFILE`
do
echo $i:$j
done  

Please help me to use multiple variables in single for loop in shell script.

Answer 1

bash allows for loops with more than one variable, but only in C like syntax:

for ((i=0,j=10;i<=j;i++,j--))
do
   echo "i=$i"
   echo "j=$j"
done

Answer 2

Maybe you actually want:

while IFS='|' read -r i j rest <&3; do
  {
    printf '%s\n' "something with $i and $j"
  } 3<&-
done 3< "$INPUTFILE"

But using a shell loop to process text is often the wrong way to go.

Here, it sounds like you just need:

awk -F '|' '{print $1 ":" $2}' < "$INPUTFILE"

Now as an answer to the question in the title, for a shell with for loops taking more than one variable, you've got zsh (you seem to already be using zsh syntax by not quoting your variables or not disabling globbing when splitting command substitution):

$ for i j in {1..6}; do echo $i:$j; done
1:2
3:4
5:6

Or the shorter form:

for i j ({1..6}) echo $i:$j

The equivalent with POSIX shells:

set -- 1 2 3 4 5 6
## or:
# IFS='
# ' # split on newline
# set -o noglob # disable globbing
# set -- $(awk ...) # split the output of awk or other command
while [ "$#" -gt 0 ]; do
  printf '%s\n' "$1:$2"
  shift 2
done

Answer 3

You can store an output of a file in a variable and then break it into two. example:

in example file contents are:

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

now script.

#!/bin/bash
for n in $(cat example)
do
    first=$(echo $n | cut -d ":" -f 1)
    second=$(echo $n | cut -d ":" -f 2)
    echo $first
    echo $second
done

Answer 4

$ cat inputfile.txt
foo|bar
baz|foobar
$ cat inputfile.txt | while IFS='|' read i j ; do echo $i:$j ; done
foo:bar
baz:foobar

this answer is a lot like this answer but it also answers the comment about not having to use file descriptors (<&3) by @sdkks

Answer 5

On embedded systems, you are often crippled on what is available. EG. for can only have one variable; awk & printf are simply not available; or IFS is not supported; etc.

In these circumstances you can achieve your goal like this:

export i=xxx
for j in `cat INPUTFILE` ; do \
    [ $i == xxx ] && export i=$j && continue ; \
    echo "$i:$j" ; \
    export i=xxx ; \
done
unset i

A more general form of this solution might look like:

export A=xxx
export B=xxx
for i in 1 2 3 4 5 6 7 8 9 10 11 ; do \
    [ $A == xxx ] && export A=$i && continue ; \
    [ $B == xxx ] && export B=$i && continue ; \
    echo "$A:$B:$i" ; \
    export A=xxx ; \
    export B=xxx ; \
done
unset A
unset B

• Assumes the string "xxx" never appears in your data-set ...If it does/might, pick something else.
• You can have any number of "fields" per "record" ...Just duplicate each of the FOUR lines which handle the fields {A, B, ...}.
• The last field is always called $i ...Feel free to add an export C=$i just before the echo if it helps.
• If the number of strings in the data-set is not a multiple of the record-size, the "remainder" (ie. |set| % |record|) will be lost.

Answer 6

GNU Parallel can often be a solution for this:

parallel -a $INPUTFILE --colsep '|' echo {1}:{2}

Answer 7

The following can be used as a one-liner inside the bash shell to iterate over two sets of variables in parallel (as zip(a, b) would do in python):

a=(x y z); b=(q w e); for i in ${!a[@]}; do echo ${a[i]}-${b[i]}; done

Answer 8

You'll need multiple loops if you want to iterate over more than one variable, like for i in 1 2 3; do for j in a b c; do ...; done; done. when the list of things to iterate over is the output of a another command, you'll need to wrap that other command in $().

Answer 9

#! /bin/bash

num="num.txt"
ch="char.txt"
int1=0

for i in `cat $num`
do
 int1=$(( $int1+1 ))

 for j in `cat $ch|tail -n +$int1`
 do
  echo $i " " $j
 break
 done

done

Output:

1   a
2   b
3   c
4   d
5   e
6   f
7   g