The ldd command will print out a list of all libraries that an executable is linked against. This is the output for a simple “Hello World” command.
20:15:31 tux@linux-v415 ($ ldd ./a.out
linux-vdso.so.1 => (0x00007fff171ff000)
libc.so.6 => /lib64/libc.so.6 (0x00007fe56ef58000)
/lib64/ld-linux-x86-64.so.2 (0x00007fe56f2e8000)
20:15:49 tux@linux-v415 ($
If you wish to view a graphical representation of your system load in an Xterm or on the text console, use the tload command. This prints the graph using text characters.
To send a broadcast message from your tty or terminal emulator window use the wall command. I tried this on my KDE desktop in the konsole window and the notification popped up from the system tray showing my message. Just type the intended message and then press Ctrl-D to send it.
10:01:58 tux@linux-v415 ($ wall
Hello
Broadcast Message from tux@linux-v4
(/dev/pts/1) at 10:02 ...
Hello
10:02:10 tux@linux-v415 ($
The lsblk command will list all of the block devices or hard disks that are mounted on your machine. This is a useful command.
10:25:09 tux@linux-v415 ($ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 465.8G 0 disk ├─sda1 8:1 0 214.9G 0 part /media/_Fedora-17-x86_6 ├─sda2 8:2 0 32.2G 0 part /media/3fabc97d-c76a-4922-8705-5536e89cfd21 ├─sda3 8:3 0 1K 0 part └─sda5 8:5 0 218.6G 0 part sdb 8:16 0 465.8G 0 disk ├─sdb1 8:17 0 430M 0 part /media/e01436e0-4aa5-420b-94aa-0b35bd00020e ├─sdb2 8:18 0 341.8G 0 part /media/c84b3630-79a5-4ab3-85a5-f50bc23a3da9 ├─sdb3 8:19 0 121.1G 0 part /media/a6f66737-afea-48c3-9694-f6da22904d37 ├─sdb4 8:20 0 1K 0 part └─sdb5 8:21 0 2.5G 0 part [SWAP] sdc 8:32 0 1.8T 0 disk └─sdc1 8:33 0 1.8T 0 part /media/Elements sdd 8:48 0 37.3G 0 disk └─sdd1 8:49 0 37.3G 0 part /media/4282F11082F10965 sr0 11:0 1 834M 0 rom /livecd loop0 7:0 0 7G 0 loop / 10:25:18 tux@linux-v415 ($
Here is an interesting command that will reverse any text fed into it. The rev command could be useful when piping text into it to reverse a text file.
10:32:21 tux@linux-v415 ($ rev Hello olleH Hello olleH
The ddate command will convert Gregorian dates into Discordian date formats. An example is shown below.
11:01:10 tux@linux-v415 ($ ddate Today is Boomtime, the 53rd day of Bureaucracy in the YOLD 3178
To see how much free RAM you have on your Linux system use the free command. This is useful to keep track of memory usage. Another way is to use the cat /proc/meminfo | grep MemFree: command.
11:01:18 tux@linux-v415 ($ free
total used free shared buffers cached
Mem: 6053668 5902464 151204 0 549500 3353780
-/+ buffers/cache: 1999184 4054484
Swap: 2559996 2240 2557756
Do you sometimes want to find where a program is installed to? The whereis command will help you with this.
11:19:15 tux@linux-v415 ($ whereis emacs emacs: /usr/bin/emacs /usr/lib/emacs /usr/bin/X11/emacs /usr/share/emacs /usr/share/man/man1/emacs.1.gz
I am not sure if I have posted this before; but the host command will print information about a certain network host. It prints all of the IP addresses and other pertinent information about the target host.
11:21:54 tux@linux-v415 ($ host localhost localhost has address 127.0.0.1 localhost has IPv6 address ::1 11:22:02 tux@linux-v415 ($ host google.com google.com has address 74.125.237.105 google.com has address 74.125.237.110 google.com has address 74.125.237.96 google.com has address 74.125.237.97 google.com has address 74.125.237.98 google.com has address 74.125.237.99 google.com has address 74.125.237.100 google.com has address 74.125.237.101 google.com has address 74.125.237.102 google.com has address 74.125.237.103 google.com has address 74.125.237.104 google.com has IPv6 address 2404:6800:4006:803::1002 google.com mail is handled by 30 alt2.aspmx.l.google.com. google.com mail is handled by 40 alt3.aspmx.l.google.com. google.com mail is handled by 50 alt4.aspmx.l.google.com. google.com mail is handled by 10 aspmx.l.google.com. google.com mail is handled by 20 alt1.aspmx.l.google.com.
To get help on the BASH shell builtin commands the help command is your friend. Type help kill to get help on the kill command for example.
11:25:33 tux@linux-v415 ($ help
GNU bash, version 4.2.10(1)-release (x86_64-suse-linux-gnu)
These shell commands are defined internally. Type `help' to see this list.
Type `help name' to find out more about the function `name'.
Use `info bash' to find out more about the shell in general.
Use `man -k' or `info' to find out more about commands not in this list.
A star (*) next to a name means that the command is disabled.
job_spec [&] history [-c] [-d offset] [n] or history -anrw [filename] or history -ps arg [arg...]
(( expression )) if COMMANDS; then COMMANDS; [ elif COMMANDS; then COMMANDS; ]... [ else COMMANDS; ] fi
. filename [arguments] jobs [-lnprs] [jobspec ...] or jobs -x command [args]
: kill [-s sigspec | -n signum | -sigspec] pid | jobspec ... or kill -l [sigspec]
[ arg... ] let arg [arg ...]
[[ expression ]] local [option] name[=value] ...
alias [-p] [name[=value] ... ] logout [n]
bg [job_spec ...] mapfile [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]
bind [-lpvsPVS] [-m keymap] [-f filename] [-q name] [-u name] [-r keyseq] [-x keyseq:shell-command] [keyseq:readlin> popd [-n] [+N | -N]
break [n] printf [-v var] format [arguments]
builtin [shell-builtin [arg ...]] pushd [-n] [+N | -N | dir]
caller [expr] pwd [-LP]
case WORD in [PATTERN [| PATTERN]...) COMMANDS ;;]... esac read [-ers] [-a array] [-d delim] [-i text] [-n nchars] [-N nchars] [-p prompt] [-t timeout] [-u fd] [name ...]
cd [-L|[-P [-e]]] [dir] readarray [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]
command [-pVv] command [arg ...] readonly [-aAf] [name[=value] ...] or readonly -p
compgen [-abcdefgjksuv] [-o option] [-A action] [-G globpat] [-W wordlist] [-F function] [-C command] [-X filterp> return [n]
complete [-abcdefgjksuv] [-pr] [-DE] [-o option] [-A action] [-G globpat] [-W wordlist] [-F function] [-C command]> select NAME [in WORDS ... ;] do COMMANDS; done
compopt [-o|+o option] [-DE] [name ...] set [-abefhkmnptuvxBCHP] [-o option-name] [--] [arg ...]
continue [n] shift [n]
coproc [NAME] command [redirections] shopt [-pqsu] [-o] [optname ...]
declare [-aAfFgilrtux] [-p] [name[=value] ...] source filename [arguments]
dirs [-clpv] [+N] [-N] suspend [-f]
disown [-h] [-ar] [jobspec ...] test [expr]
echo [-neE] [arg ...] time [-p] pipeline
enable [-a] [-dnps] [-f filename] [name ...] times
eval [arg ...] trap [-lp] [[arg] signal_spec ...]
exec [-cl] [-a name] [command [arguments ...]] [redirection ...] true
exit [n] type [-afptP] name [name ...]
export [-fn] [name[=value] ...] or export -p typeset [-aAfFgilrtux] [-p] name[=value] ...
false ulimit [-SHacdefilmnpqrstuvx] [limit]
fc [-e ename] [-lnr] [first] [last] or fc -s [pat=rep] [command] umask [-p] [-S] [mode]
fg [job_spec] unalias [-a] name [name ...]
for NAME [in WORDS ... ] ; do COMMANDS; done unset [-f] [-v] [name ...]
for (( exp1; exp2; exp3 )); do COMMANDS; done until COMMANDS; do COMMANDS; done
function name { COMMANDS ; } or name () { COMMANDS ; } variables - Names and meanings of some shell variables
getopts optstring name [arg] wait [id]
hash [-lr] [-p pathname] [-dt] [name ...] while COMMANDS; do COMMANDS; done
help [-dms] [pattern ...] { COMMANDS ; }
If you are very new to the Linux command line, the man intro command will print a helpful tutorial that will help you learn the basics.
If you want to have some fun as I did; make a copy of a text file and then use the join command to join them together…
11:30:50 tux@linux-v415 ($ join my.c my2.c #include#include #include #include clock_t times(struct tms *buf); times(struct tms *buf); int main(void) main(void) { write(1, "Hello World.\n", 15); "Hello World.\n", 15); return 0; 0; }
I am a computer enthusiast that has always been interested in maintaining and upgrading computer hardware. I was born on a farm and lived there for 13 years before moving into town. I was always interested in technology and my father always gave me good encouragement for developing my knowledge and interest in tinkering with computers. He was using a computer on the farm but that was in the very late 80`s and late 90`s. Seeing what a computer could do always fascinated me and then I knew that is what I wanted to do. The first time I used Linux was Red Hat 6.2 installed off a single CDROM and I was amazed that you did not need to install any more drivers on my old Intel Celeron machine to be able to enjoy a nice 24BPP desktop and use the GIMP to edit photos and enjoy playing the old Linux games like Xbill. Then a while later I tried Mandrake Linux 9.2 and I was hooked. It came with so much software and was very easy to use as well. Then Mandrake Linux 10 and on through FreeBSD, Debian 3.0, Debian 3.1 Suse Linux 9.2, Suse 10 and onto the Ubuntu distributions although I am using Fedora Core 15 and the Gnome 3 desktop at the moment.
