How to use Linux locate command

locate [OPTION]… [PATTERN]…

Usage: locate [OPTION]... [PATTERN]...
Search for entries in the mlocate database.
 -A, --all only show entries that match all patterns -b, --basename base file name to match unique path names -c, --count only show the number of entries found -d, --database DBPATH replace the default database (/var/lib/mlocate/mlocate.db) with DBPATH
 -e, --existing only show entries for currently existing files -L, --follow follow creeping symbolic links if the file exists (default)
 -h, --help Show this help -i, --ignore-case Ignore uppercase and lowercase differences when matching patterns -l, --limit, -n LIMIT Limit output to LIMIT items (or count) 
 -m, --mmap ignore backward compatibility -P, --nofollow, -H do not follow creeping symbolic links when checking files -0, --null separate items with NULs in output -S, --statistics do not search items, show statistics about each used database -q, --quiet do not report error messages about reading databases -r, --regexp REGEXP search for the basic regular expression REGEXP instead of pattern --regex pattern is an extended regular expression -s, --stdio ignore backward compatibility -V, --version show version information -w, --wholename match full pathnames (default)

[root@localhost ~]# locate ifconfig 
/home/oracle/app/oracle/product/11.2.0/dbhome_1/sysman/admin/scripts/ifconfig.sh
/usr/libexec/hypervkvpd/hv_set_ifconfig
/usr/sbin/ifconfig
/usr/sbin/pifconfig
/usr/share/man/de/man8/ifconfig.8.gz
/usr/share/man/fr/man8/ifconfig.8.gz
/usr/share/man/man8/ifconfig.8.gz
/usr/share/man/man8/pifconfig.8.gz
/usr/share/man/pt/man8/ifconfig.8.gz
/usr/share/man/zh_CN/man8/ifconfig.8.gz
[root@localhost ~]# 

[root@localhost ~]# locate /bin/sh
/home/oracle/app/oracle/product/11.2.0/dbhome_1/perl/bin/shasum
/usr/bin/sh
/usr/bin/sha1sum
/usr/bin/sha224sum
/usr/bin/sha256sum
/usr/bin/sha384sum

[root@localhost ~]# locate -n 3 passwd
/etc/passwd
/etc/passwd -
/etc/pam.d/passwd
[root@localhost ~]# 

[root@localhost ~]# locate -i -n 5 passwd
/etc/passwd
/etc/passwd -
/etc/pam.d/passwd
/etc/security/opasswd
/home/oracle/app/oracle/product/11.2.0/dbhome_1/apex/images/htmldb/icons/32x32/item_passwd.gif
[root@localhost ~]#

//Find files starting with /var/lib/rpm [root@localhost ~]# locate -r ^/var/lib/rpm
/var/lib/rpm
/var/lib/rpm-state
/var/lib/rpm/.dbenv.lock
/var/lib/rpm/.rpm.lock
/var/lib/rpm/Basenames
/var/lib/rpm/Conflictname
/var/lib/rpm/Dirnames
/var/lib/rpm/Group
/var/lib/rpm/Installtid

//Find the file ending with etc.conf[root@localhost ~]# locate -r etc.conf$
/usr/lib/tmpfiles.d/etc.conf
[root@localhost ~]#

# Create a new file [root@localhost ~]# touch new_file
[root@localhost ~]# locate ~/new_file
[root@localhost ~]# updatedb
[root@localhost ~]# locate ~/new_file
/root/new_file
[root@localhost ~]# 
# Delete file [root@localhost ~]# rm -rf file.txt 
[root@localhost ~]# locate ~/file.txt
/root/file.txt
[root@localhost ~]# updatedb
[root@localhost ~]# locate ~/file.txt
[root@localhost ~]#

[deng@localhost test]$ locate -S 
Database /var/lib/mlocate/mlocate.db:
    18,935 folders 231,751 files 13,753,723 bytes in file names 5,707,750 bytes used to store database [deng@localhost test]$

[root@localhost /]# locate -c passwd
183
[root@localhost /]#

[root@localhost /]# vim /etc/updatedb.conf 
[root@localhost /]#