passing strings to while loop

Question

I am trying to pass two strings to a while loop but i forgot the syntax please help me out. This is what i am trying-

#!/bin/bash
while read line
do  
    echo "successful"
done < "var1" "var2" 
exit

I know i am doing something wrong here, i used to pass strings to while loop but i forgot the syntax. Please help me out here.

I am aware of -

#!/bin/bash
while read line
do
   echo "successful"
done < "file_containing_var1_and_var2"

but i want to pass strings and not file to while loop, Any help is appreciated.

Jens · Accepted Answer · 2013-06-23 07:16:14Z

6

< redirection operator only works with files. for your requirement use a for loop

#!/bin/bash


for x in "var1" "var2"
do
   echo $x
done

edited Jun 23, 2013 at 7:16

Jens

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answered Jun 23, 2013 at 6:30

DevZer0

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Comments

jaypal singh · Accepted Answer · 2013-06-23 06:39:54Z

4

To pass string to your while loop, you need to use herestring <<< notation.

$ while read line; do 
    echo "$line"
done <<< "This is my test line"
This is my test line

answered Jun 23, 2013 at 6:39

jaypal singh

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2 Comments

user2118349 Over a year ago

Hi JS, This is exactly what i wanted. can you please point out how do i pass more than one string here.

jaypal singh Over a year ago

@user2118349 You are better off using a for loop as suggested by DevZer0, but if you must then you can do something like:

$ while IFS=: read string1 string2; do printf "%s\n%s\n" "$string1" "$string2"; done <<< "this is my string":"this is another string"

Jonathan Leffler · Accepted Answer · 2013-06-23 06:37:33Z

2

printf "%s\n" "var1" "var2" |
while read line
do  
    echo "successful: $line"
done

The printf command echoes each argument on a line on its own.

answered Jun 23, 2013 at 6:37

Jonathan Leffler

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Comments

perreal · Accepted Answer · 2013-06-23 06:33:04Z

1

You can pipe into a while loop:

#!/bin/bash
echo "var1" "var2" | while read line
do
    echo "successful: $line"
    set "$line"
    echo "v1: $1 v2: $2"
done

Output:

successful: var1 var2
v1: var1 v2: var2

answered Jun 23, 2013 at 6:33

perreal

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2 Comments

user2118349 Over a year ago

Thanks perreal, jonathan and DevZero, Your answers added something new to my vault. Thanks for your time.

glenn jackman Over a year ago

In case $line happens to begin with a hyphen, set -- $line (unquoted)

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