Searching and Extracting Data Flashcards

Which command would display only lines that do NOT match a pattern in grep?

Answer: grep -v pattern file

grep -v inverts the match, printing only lines that do not contain the pattern.

What is the default field separator used by the `sort` command?

Answer: Whitespace

By default, sort treats any whitespace (spaces or tabs) as a field separator.

Which sed command replaces only the first occurrence of 'foo' with 'bar' on each line?

Answer: sed 's/foo/bar/' file

Without the g flag, sed s/// replaces only the first match on each line.

What does `head -n 20 file.txt` display?

Answer: The first 20 lines of file.txt

head -n 20 prints the first 20 lines of the specified file.

Which command finds all files with the .conf extension under /etc?

Answer: find /etc -name '*.conf'

find /etc -name '*.conf' searches /etc for files whose names match the *.conf glob.

What does `wc -w file.txt` count?

Answer: Words in the file

wc -w counts the number of words (whitespace-delimited tokens) in the file.

Which pipe chain counts the number of unique lines in a file?

Answer: sort file | uniq | wc -l

Sorting first groups duplicates together, then uniq removes them, and wc -l counts what remains.