When working with command-line output, we often need to extract everything after a specific match. The common approach using grep -A[num] has a significant limitation:

git status | grep -A100 'Untracked files'

This requires you to guess the maximum number of lines needed, which is neither elegant nor reliable for automation.

Here are more robust methods to capture all lines after a match:

1. Using AWK for Flexible Extraction

git status | awk '/Untracked files/{flag=1;next} flag'

How this works:

• /Untracked files/ triggers when the pattern is found
• flag=1 sets a marker
• next skips printing the match line itself
• flag prints all subsequent lines when flag is true

2. Sed Solution for Stream Editing

git status | sed -n '/Untracked files/,$p'

Key points:

• -n suppresses automatic printing
• /pattern/,$ selects from match to end of file
• p prints the selection

When working specifically with git output, we can create more targeted solutions:

git status --porcelain | grep '^??'

Or for detailed output:

git status --untracked-files=all --porcelain

These techniques work beyond just git status:

# For config files:
cat /etc/nginx/nginx.conf | awk '/http {/{flag=1;next} flag'

# For log files:
journalctl -u nginx | sed -n '/Error/,$p'

For large files (100MB+), these alternatives perform better than grep:

# Using Perl for efficiency
perl -ne 'print if $found ||= /Untracked files/' largefile.log

# Using tail for known positions
grep -n 'Untracked files' file | cut -d: -f1 | xargs -I{} tail -n +{} file

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When working with command-line tools like git status, we often need to extract specific portions of the output. The common approach using grep -A requires specifying an exact number of lines to display after the match, which isn't ideal when we don't know how many lines will follow.

The sed stream editor provides a more elegant solution for this task:

git status | sed -n '/Untracked files/,$p'

This command works by:

• -n suppresses automatic printing
• /Untracked files/,$ defines a range from the matching line to end of file
• p prints the matched range

For more complex parsing needs, awk offers additional flexibility:

git status | awk '/Untracked files/{flag=1;next} flag'

This approach:

• Sets a flag when the pattern is matched
• Uses next to skip printing the match line itself
• Prints all subsequent lines while the flag is set

For production scripts, consider these improvements:

# Case-insensitive matching
git status | sed -n '/[Uu]ntracked files/,$p'

# Excluding the match line itself
git status | sed -n '/Untracked files/{n;:a;p;n;ba}'

For large outputs, sed generally performs better than awk for simple range extraction. Benchmark with:

time git status | sed -n '/Untracked files/,$p' > /dev/null
time git status | awk '/Untracked files/{flag=1;next} flag' > /dev/null