Quick Shell Tricks to Remove Blank Lines from Logs with grep, sed, awk, tr, and vi

The author reflects on the saying "scripts are fiercer than tigers," noting that scripts are powerful yet error‑prone, and that shell scripts are ideal for quick prototypes and log processing in embedded development.

1. grep

Use $ grep -v '^$' file to output only non‑empty lines. The -v flag inverts the match, selecting lines that do not match the regular expression. The caret ^ anchors the start of a line and $ anchors the end.

2. sed

The stream editor sed can delete blank lines with $ sed '/^$/d' file. The pattern ^$ matches empty lines, and the d command deletes them. See man sed for more options.

3. awk

Awk can filter out empty lines using $ awk '!/^$/' file. Awk processes each line, and the default action is print, so the command prints only lines that do not match ^$. Awk programs consist of pattern { action } pairs.

4. tr

The translate utility tr can squeeze repeated newline characters: $ cat in.txt | tr -s '\n'. The -s (squeeze‑repeats) option collapses consecutive identical characters into a single instance.

5. vi

Within the vi editor, the command :g/^$/d globally searches for empty lines ( ^$) and deletes them ( d).

These five methods provide a variety of ways to remove blank lines from logs, each suited to different workflows and preferences.

The author plans future articles covering shell script fundamentals, tips, coding standards, and analyses of open‑source shell projects.