i wanted to read two files from stdin in "while do nested loop" like file 1 first line and then process all file 2 input lines and then file 1 second line and process all lines from file 2 and so on.
example code
#!/bin/bash
cd ~/files/ ;
while read line1;
do
echo "$line1"output;
while read line2;
do
echo $line1;
echo $line2;
echo "$line1"test"line2" | tee -a output.txt ;
done < "${1:-/dev/stdin}" ;
i am reading file input from stdin using ./script.sh file1.txt but i wanted to input two files like
./script.sh file1.txt file2.txt i tried done < "${1:-/dev/stdin}" ; done < "${2:-/dev/stdin}" ; its not working . also tried file descripters like while read line1<&7; while read line2<&8; input like ./script.sh file1.txt 7< file2.txt 8 and it throws bad file descriptor error .
To get access to both files within the inner loop, open them on different file descriptors. Here's an example using FD #3 and #4:
#!/bin/bash
while read line1 <&3; do # Read from FD #3 ($1)
while read line2 <&4; do # Read from FD #4 ($2)
echo "line1: $line1, line2: $line2"
done 4<"${2:-/dev/stdin}" # Read from $2 on FD #4
done 3<"${1:-/dev/stdin}" # Read from $1 on FD #3
Here's an example run:
$ cat file1.txt
one
two
$ cat file2.txt
AAA
BBB
$ ./script.sh file1.txt file2.txt
line1: one, line2: AAA
line1: one, line2: BBB
line1: two, line2: AAA
line1: two, line2: BBB
BTW, a few other recommendations: You should (almost) always put variable references in double-quotes (e.g. echo "$line1" instead of echo $line1) to avoid weird parsing. You don't need semicolons at the end of lines (I used them in the while ... ; do statements above, but only because I put the do on the same line). And you should (almost) always check for error when using cd in a script (so it doesn't just keep running in the wrong place, with unpredictable results).
shellcheck.net is good at pointing out common scripting mistakes; I recommend it!