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Information Commands

apropos subject shows commands related to subject (ex: apropos floppy)
If it never finds anything, update db with “mandb”as root.
cal displays a calendar (ex: “cal 2004” to see all of 2004)
date prints or the system’s date and time
df
lists the amount of diskspace used and available. Putting “.”
after the command lists the diskspace on the partition you are
using right then. Use –h to convert bytes to KB, MB, GB.
dmesg quick view of the boot log from the last system boot
du gives the amount of diskspace taken by the directory. Try -h
free gives the amount of memory available
history displays the last commands that you issued at the prompt
hostname prints the name of the machine used
id prints information about the user/owner of shell
info command similar to the man command but with hyperlinking available
last username displays information about previous logins of username
ldd program lists the shared libraries required by program
lsattr file lists the file attributes of a given file
lsmod lists all loaded kernel modules
lspci lists all PCI devices
lsusb lists all USB devices
man -k command gives more information about different commands. -k gives
the manuals that contain information about the keyword
ps lists the active processes running in your account (try “ps -ef”)
rpm –q program tells you whether program is installed or not (and version)
sdiff file1 file2 compares file1 to file2 and prints the lines that differ
stty shows and sets terminal characteristics
top displays in real-time a list of running tasks
tty prints the tty of a shell
uname displays information about the operating system
uptime displays the uptime of the machine and the load it carries
whatis command summary of command (run makewhatis to build DB)
whoami (sometimes “who am i”) gives your username, tty and time the shell was started

xwininfo print information on the window you click (X-Windows only)
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