Finding files

On Macs and PCs, powerful tools exist for finding files that match certain criteria, or contain certain text.

Two Unix commands that provide similar capabilities are find and grep.

find looks for files based on their attributes (name, type, size, date), searches recursively (through all subdirectories of a given directory), and returns a list of file names.

grep looks for files based on their contents, searching locally by default (but can be made to search recursively), and returns a list of lines that contain the searched-for pattern.

Like many Unix commands, find and grep have many options that expand their capabilities, and can be combined with other Unix commands using pipes (|) and redirection (>) to perform complex tasks.

Tutorials exist for Unix, grep, and find. Google searches on these commands are often helpful (e.g., "Unix how to find and delete large files"). Here are a few examples of each.

Searching for Files (find)

Find all files with name that matches a pattern:

find . -name "*.trr"

Find files above a certain size:

find . -type f -size +100G

Find has a powerful option -exec, which executes a command on files that are found.
Use this with caution! List the files first.

Find files, and then compress them:

find . -name "*.trr" -exec compress {} \; 

Find files of a certain type, get their sizes, and sum them:

find . -name "*.trr" -exec du -csh '{}' +

Find files of a certain type, get their sizes, and sort by size:

find . -name "*.trr" -exec du -sh '{}' + | sort -h -r

Find files above a certain size and list them:

find . -type f -size +100G -exec ls -lh {} +

Find files of a certain extension and delete them:

find . -name "*.trr" -exec rm -f {} +

Searching In Files (grep)

In its simplest form, grep searches for a "pattern" in a given file or set of files:

grep <pattern> <file>

In this form, grep finds all lines in <file> that contain <pattern>. The pattern can have "wildcards" -- * matches anything, for example.

<file> can be a single filename, or itself a pattern that matches multiple files; for example, *.log matches all log files.

grep is often useful to "filter" the output of commands. ps -e lists all running processes (a very long list). To look for any process that mentions vmd:

ps -e | grep vmd

grep -R ‘.’ --include *.sh -e ‘sed’ > sedExamples