在bash中读取一行

Question

I am using the below code to read a file word by word in bash

while read line; do
    for word in $line; do
    echo "word = '$word'"
    done
done  < My_File

However, the above code does not work since My_File has only a single line. How should I modify the code?

Answer 1

Reading Into An Array

This reads a single line into an array, splitting on characters in IFS (by default, spaces tabs and newlines).

read -r -a words <My_File || (( ${#words[@]} ))
for word in "${words[@]}"; do
  echo "Read word: $word"
done

The || condition prevents set -e (which you shouldn't be using anyhow ) from causing the script to exit if there's no terminating newline.

---

Reading With A Space Delimiter

Note that this one works only if a regular space, and no other character, separates your words. If you want tabs instead, change -d ' ' to -d $'\\t' .

while IFS='' read -r -d ' ' word; word=${word%$'\n'}; [[ $word ]]; do
  echo "Read word: $word"
done <My_File

word=${word%$'\\n'} strips any newline which may be present if your file wasn't in exactly the (space-delimiter-only) format given.

Answer 2

You could adjust your code like this to account for lines without a terminating newline character:

(cat My_File; echo ) | while read line; do
    for word in $line; do
    echo "word = '$word'"
    done
done

This will add a newline at the end of the input, which won't change the output regardless of whether My_File has a newline or not.

-Rich Alloway (RogueWave)