Searching Files & Directories: find, locate, grep

Searching for files and directories in Linux is an essential skill, whether you’re an administrator, developer, or casual user. Linux provides powerful tools like find, locate, and grep to help you quickly and efficiently search for files and their contents. This tutorial covers these commands in detail.

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1. find – Searching for Files & Directories

The find command searches for files and directories in a directory hierarchy. It is highly flexible and allows searching by name, type, size, modification time, and more.

Basic Syntax

find [path] [expression]

Common find Usage Examples

1.1 Find a file by name

find /home -name "file.txt"

• Searches for file.txt in the /home directory and its subdirectories.
• -name makes the search case-sensitive.

1.2 Case-insensitive search

find /home -iname "file.txt"

• -iname makes the search case-insensitive.

1.3 Find directories

find / -type d -name "Documents"

• Searches for directories (-type d) named “Documents”.

1.4 Find files by extension

find /var/log -type f -name "*.log"

• Searches for all log files (*.log) in /var/log.

1.5 Find files by size

find / -size +100M

• Finds files larger than 100MB.
• Use -size -100M for files smaller than 100MB.

1.6 Find files modified in the last 7 days

find /home -mtime -7

• -mtime -7 finds files modified in the last 7 days.
• -mtime +7 finds files older than 7 days.

1.7 Find files accessed in the last 24 hours

find /var/log -atime -1

• -atime -1 finds files accessed in the last day.

1.8 Find and delete files

find /tmp -type f -name "*.tmp" -delete

• Deletes all .tmp files in /tmp.

1.9 Find files with specific permissions

find / -type f -perm 644

• Searches for files with 644 permissions.

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2. locate – Fast File Searching

The locate command is much faster than find because it searches a pre-built database instead of scanning the file system.

Installing locate

sudo apt install mlocate   # Debian/Ubuntu
sudo yum install mlocate   # CentOS/RHEL

After installing, update the database:

sudo updatedb

Basic Usage

2.1 Find a file by name

locate file.txt

• Searches for file.txt across the system.

2.2 Case-insensitive search

locate -i file.txt

2.3 Find files with a specific extension

locate "*.log"

2.4 Limit search results

locate -n 10 "*.log"

• Shows only the first 10 results.

2.5 Find recently modified files

sudo updatedb && locate file.txt

• Updates the database before searching (useful if files were recently created or moved).

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3. grep – Searching Inside Files

The grep command is used to search for text inside files.

Basic Syntax

grep [options] "pattern" file

Common grep Usage Examples

3.1 Search for a word in a file

grep "error" /var/log/syslog

• Searches for “error” in /var/log/syslog.

3.2 Case-insensitive search

grep -i "error" /var/log/syslog

3.3 Search in multiple files

grep "error" /var/log/*.log

• Searches for “error” in all .log files in /var/log.

3.4 Show line numbers

grep -n "error" /var/log/syslog

• Displays the line numbers where “error” is found.

3.5 Recursive search (search in directories)

grep -r "error" /var/log

• Searches for “error” in all files within /var/log.

3.6 Invert match (show lines without the pattern)

grep -v "error" /var/log/syslog

• Shows lines that do NOT contain “error”.

3.7 Use regex in search

grep -E "error|fail|warn" /var/log/syslog

• Searches for “error”, “fail”, or “warn”.

3.8 Count the number of matches

grep -c "error" /var/log/syslog

• Displays the number of times “error” appears.

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Conclusion

• Use find for precise, real-time searches based on file attributes.
• Use locate for lightning-fast searches using a pre-built database.
• Use grep for searching inside files for text patterns.

Each tool has its strengths, so use the one that fits your needs best! 🚀