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Open the two files on different file descriptors. Redirect the input of the read built-in to the descriptor that the file you want is connected to. In bash/ksh/zsh, you can write read -u 3 instead of read <&3.

while IFS= read -r lineA && IFS= read -r lineB <&3; do
  echo "$lineA"; echo "$lineB"
done <fileA 3<fileB

This snippet stops when the shortest file has been processed. See Reading two files into an IFS while loop -- Is there a way to get a zero diff result in this case? if you want to keep processing until the end of both files.

See also When would you use an additional file descriptor? for additional information on file descriptors, and Why is `while IFS= read` used so often, instead of `IFS=; while read..`? for an explanation of IFS= read -r.

Open the two files on different file descriptors. Redirect the input of the read built-in to the descriptor that the file you want is connected to. In bash/ksh/zsh, you can write read -u 3 instead of read <&3.

while IFS= read -r lineA && IFS= read -r lineB <&3; do
  echo "$lineA"; echo "$lineB"
done <fileA 3<fileB

This snippet stops when the shortest file has been processed. See Reading two files into an IFS while loop -- Is there a way to get a zero diff result in this case? if you want to keep processing until the end of both files.

See also When would you use an additional file descriptor? for additional information on file descriptors, and Why is `while IFS= read` used so often, instead of `IFS=; while read..`? for an explanation of IFS= read -r.

Open the two files on different file descriptors. Redirect the input of the read built-in to the descriptor that the file you want is connected to. In bash/ksh/zsh, you can write read -u 3 instead of read <&3.

while IFS= read -r lineA && IFS= read -r lineB <&3; do
  echo "$lineA"; echo "$lineB"
done <fileA 3<fileB

This snippet stops when the shortest file has been processed. Replace read … && read … by read … || read … if you want to keep processing the longest file ($lineA will be empty if you keep processing fileB and vice versa). Use IFS= read -r lineA; IFS= read -r lineB; if you want to process till the end of fileB.

See also When would you use an additional file descriptor? for additional information on file descriptors, and Why is `while IFS= read` used so often, instead of `IFS=; while read..`? for an explanation of IFS= read -r.

Open the two files on different file descriptors. Redirect the input of the read built-in to the descriptor that the file you want is connected to. In bash/ksh/zsh, you can write read -u 3 instead of read <&3.

while IFS= read -r lineA && IFS= read -r lineB <&3; do
  echo "$lineA"; echo "$lineB"
done <fileA 3<fileB

This snippet stops when the shortest file has been processed. See Reading two files into an IFS while loop -- Is there a way to get a zero diff result in this case? if you want to keep processing until the end of both files.

See also When would you use an additional file descriptor? for additional information on file descriptors, and Why is `while IFS= read` used so often, instead of `IFS=; while read..`? for an explanation of IFS= read -r.

Open the two files on different file descriptors. Redirect the input of the read built-in to the descriptor that the file you want is connected to. In bash/ksh/zsh, you can write read -u 3 instead of read <&3.

count=1
while IFS= read -r lineA && IFS= read -r lineB <&3; do
  echo "$lineA"; echo "$lineB"
done <fileA 3<fileB

This snippet stops when the shortest file has been processed. Replace read … && read … by read … || read … if you want to keep processing the longest file ($lineA will be empty if you keep processing fileB and vice versa). Use IFS= read -r lineA; IFS= read -r lineB; if you want to process till the end of fileB.

See also When would you use an additional file descriptor? for additional information on file descriptors, and Why is `while IFS= read` used so often, instead of `IFS=; while read..`? for an explanation of IFS= read -r.

Open the two files on different file descriptors. Redirect the input of the read built-in to the descriptor that the file you want is connected to. In bash/ksh/zsh, you can write read -u 3 instead of read <&3.

while IFS= read -r lineA && IFS= read -r lineB <&3; do
  echo "$lineA"; echo "$lineB"
done <fileA 3<fileB

This snippet stops when the shortest file has been processed. Replace read … && read … by read … || read … if you want to keep processing the longest file ($lineA will be empty if you keep processing fileB and vice versa). Use IFS= read -r lineA; IFS= read -r lineB; if you want to process till the end of fileB.

See also When would you use an additional file descriptor? for additional information on file descriptors, and Why is `while IFS= read` used so often, instead of `IFS=; while read..`? for an explanation of IFS= read -r.