Master Linux File Search: which, whereis, locate & find Commands Explained

Finding the Absolute Path of a Command

The which command displays the absolute path of a given executable, using the PATH environment variable.

[root@localhost ~]# which bash
/usr/bin/bash

[root@localhost ~]# which ls
alias ls='ls --color=auto'
/usr/bin/ls

Locating Specific Files with whereis

whereis

locates the binary, source, and manual pages of a program name.

[root@localhost ~]# whereis --help
# syntax: whereis [options] filename
-b   # search only binaries
-m   # search only man pages
-s   # search only source files

Example:

[root@localhost ~]# whereis -b ifconfig
ifconfig: /usr/sbin/ifconfig

[root@localhost ~]# whereis -m ifconfig
ifconfig: /usr/share/man/man8/ifconfig.8.gz

Using locate and Updating Its Database

The locate command searches a pre‑built database ( /var/lib/mlocatedb) that is updated daily; use updatedb to refresh it manually.

[root@localhost ~]# yum install -y mlocate
[root@localhost ~]# updatedb
[root@localhost ~]# locate /etc/passwd
/etc/passwd
/etc/passwd-

Comprehensive Searches with find

The find command offers extensive options for locating files by name, size, type, permissions, timestamps, inode, and more.

# Basic syntax: find [path] [expression]
-name "*.log"          # by filename pattern
-size -10k              # files smaller than 10 KB
-size +1M               # files larger than 1 MB
-type f                 # regular files
-type d                 # directories
-type l                 # symbolic links
-perm 0644              # exact permission bits
-user wang              # owned by user "wang"
-ctime +7               # changed more than 7 days ago
-mmin -120              # modified within last 120 minutes
-inum 1024 -exec rm {} \;   # delete by inode number
-a -o                    # logical AND / OR
-exec ls -l {} \;       # execute a command on each match

Examples:

# Find all .log files under /var
find /var/ -name "*.log"

# Find .txt files named 1‑3 in /root
find /root/ -name "[1-3].txt"

# Find files in /etc smaller than 10 KB
find /etc/ -size -10k

# Find files larger than 1 MB in /etc
find /etc/ -size +1M

# Find files owned by user "wang" in /root
find /root/ -user wang

# Find files with permission 0644 in /boot
find /boot/ -perm 0644

# Find binary files in /usr/bin
find /usr/bin/ -type f

# Find files modified in the last 120 minutes in /etc
find /etc/ -mmin -120

# Find files changed more than 7 days ago in /etc
find /etc/ -ctime +7

# Delete files with inode 1024
find ./ -inum 1024 -exec rm {} \;

# Find files between 1 KB and 10 KB in /etc
find /etc/ -size +1k -a -size -10k

# List .log files in /var/log and show details
find /var/log/ -name "*.log" -exec ls -l {} \;

# List files starting with "init" in /etc, exclude directories
find /etc/ -name "init*" -a -type f -exec ls -l {} \;

# Delete yum.log in /tmp
find /tmp/ -name yum.log -exec rm {} \;

# Delete all files owned by user lyshark (prompt before each)
find / -user lyshark -ok rm -r {} \;

Logical Operators

Use -a (AND) and -o (OR) to combine multiple criteria.

# Example: files larger than 1 KB AND smaller than 10 KB
find /etc/ -size +1k -a -size -10k

These commands together provide a powerful toolkit for locating and managing files on Linux systems.