apt (advanced package tool) commands

apt (advanced package tool) commands:
1. apt-cache
     pkgnames,        list all package names
     search php,       search for php packages
2. apt-get install php4-mysql,        install mysql extension for php4
    apt-get install php4-curl
    apt-get install php4-gd
3. dpkg - purge wu-ftpd,     erase all the data about wu-ftpd
4. rename 'y/A-Z/a-z/' *
    or rename 'tr/A-Z/a-z/' *
    rename all the name of files to lower case.