CIS241

System-Level Programming and Utilities

grep and wildcards

Erik Fredericks, frederer@gvsu.edu
Fall 2025

Based on material provided by Erin Carrier, Austin Ferguson, and Katherine Bowers

grep - pattern-matching search/filter

Usage: grep string filename

Common options:

• -w: Search only whole words
  • Removes partial matches, -w abc does not match abcdef
• -r: recursive (search files in directory)
• -i: ignore case
• -n: print line number

More with regex (later)

Wildcards

Probably have talked about these already, but formally...

Pattern matching for filenames!

• * - matches any number of characters
  • ls *.txt
• ? - matches any single character
  • ls data_?.csv
    • Matches data_7.csv but not data_17.csv

Wildcards

• [] - character class or range

  • [abc], [a-z], [[:upper:]], etc...
    • Note the range is per character
  • [!a] for complement
    • ls [[:upper:]]*

• This is all called globbing!

  • man 7 glob

https://tldp.org/LDP/abs/html/globbingref.html

Some practice!

Pop open the manual on glob --> man glob

• Remember, q gets you out of it

Oh no we have some things to look for!

Some practice - search for the following phrases

• Search for: save processing time

  • man glob | grep "save processing time"

• Search for: all uppercase words

  • man glob | grep "[[:upper:]]"

• Search for glob()

  • man glob | grep "glob()"

More practice!

Create a temporary directory

• mkdir temp
• cd temp

Create some files in it

for i in {1..200}
do
  touch "file_$i"
done

ls

More practice!

List all files that start with f:

• ls f*

List all files that start with file_50:

• ls file_50*

List all files in the range of 5-99:

• Oops need brace expansion -- only 1 character handled at a time
• ls file_{[5-9],[1-9][0-9]}
  • This says, either file 5-9, or file 10-99