The following reads a file passed as an argument line by line:
while IFS= read -r line; do echo "Text read from file: $line" done < my_filename.txt
This is the standard form for reading lines from a file in a loop. Explanation:
IFS='') prevents leading/trailing whitespace from being trimmed.
-rprevents backslash escapes from being interpreted.
Or you can put it in a bash file helper script, example contents:
#!/bin/bash while IFS= read -r line; do echo "Text read from file: $line" done < "$1"
If the above is saved to a script with filename
readfile, it can be run as follows:
chmod +x readfile ./readfile filename.txt
If the file isn’t a standard POSIX text file (= not terminated by a newline character), the loop can be modified to handle trailing partial lines:
while IFS= read -r line || [[ -n "$line" ]]; do echo "Text read from file: $line" done < "$1"
|| [[ -n $line ]] prevents the last line from being ignored if it doesn’t end with a
read returns a non-zero exit code when it encounters EOF).
If the commands inside the loop also read from standard input, the file descriptor used by
read can be chanced to something else (avoid the standard file descriptors), e.g.:
while IFS= read -r -u3 line; do echo "Text read from file: $line" done 3< "$1"
(Non-Bash shells might not know
read -u3; use
read <&3 instead.)