Reading a text file

How to:

Here’s the simplest way to read a file line-by-line:

while IFS= read -r line; do
    echo "Text: $line"
done < "yourfile.txt"

Want the whole file at once? Try this:

echo "$file_content"

Or do you need a specific line, say line 4?

sed '4q;d' yourfile.txt

Sample output for reading line 4:

This is the content of line four.

Deep Dive

Back in the day, we didn’t have fancy IDEs, we had terminals and simple text editors. UNIX tools were designed with a philosophy of doing one thing well. cat, less, sed, and awk are veterans at manipulating text.

Reading a file in Bash leverages these tools, plus Bash’s own redirects and loops. For example, using while with read is good for memory efficiency with large files. You’re reading line by line, not dumping everything in memory.

sed is a stream editor. Grabbing a specific line with sed '4q;d' yourfile.txt tells sed to quit after line 4 (4q) and then print (;d) that line.

Alternatives exist. awk is powerful for text processing. Perl and Python scripts can be invoked within Bash when text processing gets complex. Each of these tools and languages has its own use cases and performance considerations.

See Also

  1. Bash Scripting Guide:
  2. sed and awk 101 Hacks:
  3. Linux Command Line Text Processing with grep, awk, sed, sort, and friends: