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CLI Magic: Information, please
By Joe Barr
on
July 25, 2005 (8:00:00 AM)
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There are lots of ways the CLI can help you. Often, you don't need to do something so much as you need to know something. This week we'll take a quick look at several commands --
whereis, whatis, df, kernelversion, ifconfig, route, and last -- that can quickly answer questions about your system or configuration. Wipe that GUI mess out of your eyes and meet me at the CLI.
Where is that darn command?
You know the command is on your system, because you've used it before. But now you can't remember where it lives. Is it in /sbin? Or /usr/bin? Somewhere else? The whereis command is designed to answer that very question. In fact, whereis will tell you not only where to find the executable command, but the source code -- if it's present -- and man pages as well. All you need to do is ask, by providing the name of the command you're looking for:
warthawg@linux:~> whereis whatis whatis: /usr/bin/whatis /usr/share/man/man1/whatis.1.gz
What is that command for?
Maybe you've heard people mention a command, but aren't sure what it does. All you have to is ask. Here's a metaphysical example to consider:
warthawg@linux:~> whatis time time (1) - time a simple command or give resource usage time (2) - get time in seconds time (n) - Time the execution of a script time (1p) - time a simple command time (3p) - get time
How much disk space do I have left?
An excellent question to ask from time to time, and especially before a critical drive fills up completely. To get the answer, type df on the command line. This handy little utility shows you how much space you've used and how much is left in every mounted file system. Like this:
warthawg@linux:~> df Filesystem 1K-blocks Used Available Use% Mounted on /dev/hdc1 19550436 3493984 16056452 18% tmpfs 517572 0 517572 0% /dev/shm /dev/hda2 7847500 32840 7814660 1% /downloads /dev/hdd1 115380192 39944740 69574416 37% /home
I'm running the 2.4 kernel, what about you?
If you hang around Linux people very long, whether it's a LUG meeting or online chat, someone is going to ask what version of the kernel you're running. There's a command to tell, just in case you forget:
warthawg@linux:~> /sbin/kernelversion 2.6
What's my IP address?
Sometimes you just have to know your IP address. Entering ifconfig without any arguments is one way to find out, and learn a lot more as well:
warthawg@linux:~> /sbin/ifconfig
eth0 Link encap:Ethernet HWaddr 00:50:8D:4E:9D:D0
inet addr:192.168.0.101 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::250:8dff:fe4e:9dd0/64 Scope:Link
UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
RX packets:74969 errors:0 dropped:0 overruns:0 frame:0
TX packets:76379 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:54194289 (51.6 Mb) TX bytes:12136154 (11.5 Mb)
Interrupt:11 Base address:0xe800
How do I get to the Internet from here?
OK, you found out what your IP address is -- even if it is private, like the one above -- but how do you talk to the Internet? The route command can give you the answer. No arguments required:
warthawg@linux:~> /sbin/route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.0.0 * 255.255.255.0 U 0 0 0 eth0 link-local * 255.255.0.0 U 0 0 0 eth0 loopback * 255.0.0.0 U 0 0 0 lo default 192.168.0.1 0.0.0.0 UG 0 0 0 eth0
As you can see, my default gateway has an IP address of 192.168.0.1. In my case, that's my router, which talks to the LAN on one side and to the cable modem/Internet on the other.
At last
Last we have last. Enter it without any arguments and it will show you the last system signons to your system, going as far back as the log files allow it to go. The output looks like this:
warthawg pts/0 :0.0 Mon Jul 18 16:43 still logged in warthawg pts/0 :0.0 Mon Jul 18 16:42 - 16:42 (00:00) warthawg pts/0 :0.0 Mon Jul 18 16:40 - 16:40 (00:00) warthawg pts/3 :0.0 Mon Jul 18 15:35 - 15:39 (00:04) warthawg pts/2 :0.0 Mon Jul 18 14:47 still logged in warthawg pts/0 :0.0 Mon Jul 18 14:36 - 16:34 (01:58) warthawg pts/0 :0.0 Mon Jul 18 14:23 - 14:36 (00:13) warthawg pts/0 :0.0 Mon Jul 18 14:20 - 14:23 (00:02) warthawg pts/2 :0.0 Mon Jul 18 14:07 - 14:18 (00:11) warthawg pts/2 :0.0 Mon Jul 18 13:44 - 13:45 (00:01) warthawg pts/0 :0.0 Mon Jul 18 11:52 - 14:07 (02:15)
There you have it. A tease on seven different commands you can use to get information about your system. Many of them allow arguments that you can use to tune and modify the output. If any of these have caught your fancy, do the man thing.
Comments
on CLI Magic: Information, pleaseNote: Comments are owned by the poster. We are not responsible for their content.
missing commands that should have been mentioned
Posted by: Anonymous Coward on July 25, 2005 05:59 PM
These are simple commands that could have been mentioned:
which - shows the full path of the executable that would be executed. Useful to disambiguate if there are different executables in different paths with the same name.
uname - print system information. Use as
$ uname -a
to print all information
whoami - print currently used login. Useful when you are jumping via ssh from one system to another
hostname - print name of the host.
finger - report information about users on local and remote machines
file - report information about the type of a certain file.
lpq/lpstat - report status of print jobs
ps - show active processes in the system.
who - reports which users are logged in<nobr> <wbr></nobr>...
which - shows the full path of the executable that would be executed. Useful to disambiguate if there are different executables in different paths with the same name.
uname - print system information. Use as
$ uname -a
to print all information
whoami - print currently used login. Useful when you are jumping via ssh from one system to another
hostname - print name of the host.
finger - report information about users on local and remote machines
file - report information about the type of a certain file.
lpq/lpstat - report status of print jobs
ps - show active processes in the system.
who - reports which users are logged in<nobr> <wbr></nobr>...
Re:missing commands that should have been mentione
Posted by: Anonymous Coward on July 26, 2005 12:51 AM
If you're looking for unix commands, try <a href="http://www.coolcommands.com/" title="coolcommands.com">http://www.coolcommands.com/</a coolcommands.com>
whereis is alright,<nobr> <wbr></nobr>/if/ you're after all that information. What if you just want the first bit of information, the path of the executable? This is why we have which:
which whatis<nobr> <wbr></nobr>/usr/bin/whatis
And ofcourse df can be made more useful with the -h switch - it presents the sizes in figures that are a bit more human-readable: MBs/GBs where appropriate instead of KBs... I have a 30GB drive. This is quite small by today's standards. Why would I look at the used space on it in terms of kilobytes?
which whatis<nobr> <wbr></nobr>/usr/bin/whatis
And ofcourse df can be made more useful with the -h switch - it presents the sizes in figures that are a bit more human-readable: MBs/GBs where appropriate instead of KBs... I have a 30GB drive. This is quite small by today's standards. Why would I look at the used space on it in terms of kilobytes?
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I don't have that command in my linux box.. maybe there are some exceptions.<nobr> <wbr></nobr>:D
Some distros have more or less commands included by default. Try uname -a instead. It even gives more info.
And, just a personal comment. I can't stand to find that a distro do not include grep or locate by default. It is really frustrating.
And, just a personal comment. I can't stand to find that a distro do not include grep or locate by default. It is really frustrating.
uname -r
lists also the kernel version
lists also the kernel version
Not all distributions include locate by default. But it is really usefull.
Example: locate *HOWTO*
Finds all files that cointain the word HOWTO.
And grep & rgrep can be usefull too. Lets say that you are looking for al the files that opens a Mysql connection in your source code. Lets type
rgrep mysql_connect . ( assuming that al the source is in the directory . or subdirectories...)
I will look _inside_ the files. It's absolutely a time saver command.
Example: locate *HOWTO*
Finds all files that cointain the word HOWTO.
And grep & rgrep can be usefull too. Lets say that you are looking for al the files that opens a Mysql connection in your source code. Lets type
rgrep mysql_connect . ( assuming that al the source is in the directory . or subdirectories...)
I will look _inside_ the files. It's absolutely a time saver command.
locate/slocate require you to build a database of information before you can use them. Most distro's have an "updatedb" command which must be run as root before locate will work.
NB -- If your distro includes/installs locate, it will most likely put updatedb into a cron job and run it for you, every night. This is fine on a desktop where files constantly come and go, but if you run a server with a ton of files, updatedb can bring your system to a screeching halt everynight for as long as it takes to run. In production environments, updatedb's cron job is best disabled, and updatedb run only when needed. At the very least, learn what the '-e' flag does to (GNU) updatedb.
NB -- If your distro includes/installs locate, it will most likely put updatedb into a cron job and run it for you, every night. This is fine on a desktop where files constantly come and go, but if you run a server with a ton of files, updatedb can bring your system to a screeching halt everynight for as long as it takes to run. In production environments, updatedb's cron job is best disabled, and updatedb run only when needed. At the very least, learn what the '-e' flag does to (GNU) updatedb.
Example:
$ apropos alsa
aconnect (1) - ALSA sequencer connection manager
alsaconf (8) - configuration tool for the Advanced Linux Sound Architecture
alsactl (1) - advanced controls for ALSA soundcard driver
alsamixer (1) - soundcard mixer for ALSA soundcard driver, with ncurses interface
amidi (1) - read from and write to ALSA RawMIDI ports
amixer (1) - command-line mixer for ALSA soundcard driver
aplay (1) - command-line sound recorder and player for ALSA soundcard driver
arecord (1) - command-line sound recorder and player for ALSA soundcard driver
aseqnet (1) - ALSA sequencer connectors over network
speaker-test (1) - command-line speaker test tone generator for ALSA
$ apropos alsa
aconnect (1) - ALSA sequencer connection manager
alsaconf (8) - configuration tool for the Advanced Linux Sound Architecture
alsactl (1) - advanced controls for ALSA soundcard driver
alsamixer (1) - soundcard mixer for ALSA soundcard driver, with ncurses interface
amidi (1) - read from and write to ALSA RawMIDI ports
amixer (1) - command-line mixer for ALSA soundcard driver
aplay (1) - command-line sound recorder and player for ALSA soundcard driver
arecord (1) - command-line sound recorder and player for ALSA soundcard driver
aseqnet (1) - ALSA sequencer connectors over network
speaker-test (1) - command-line speaker test tone generator for ALSA
Apropos, like the locate entry above, is a useful tool, but it requires you to build a database for it to work. Most distro's that use apropos use "makewhatis" to build the whatis db from existing man pages in the man path,usually in a cron job.
"whatis" (mentioned in the article itself) and "apropos" both work from the whatis database. "apropos" searches whatis for strings, "whatis" searches for complete words.
NB -- You can get the same functionality that apropos gives you by using "man -k"
"whatis" (mentioned in the article itself) and "apropos" both work from the whatis database. "apropos" searches whatis for strings, "whatis" searches for complete words.
NB -- You can get the same functionality that apropos gives you by using "man -k"
An excellent question to ask from time to time, and especially before a critical drive fills up completely. To get the answer, type df on the command line.
But what's taking up all that diskspace? 'du' provides the anwser:
[todsah@jib]~$ whatis du
du (1) - estimate file space usage
[todsah@jib]~$ du -hs *
93M Mail
32M Trash
426M bin
108M dev
357M download
1.8M notes
4.0K temp
And though it's not a CLI tool, XDU is still very handy. It shows a graphical representation of the output of the 'du' command:
<a href="http://sd.wareonearth.com/~phil/xdu/" title="wareonearth.com">http://sd.wareonearth.com/~phil/xdu/</a wareonearth.com>
But what's taking up all that diskspace? 'du' provides the anwser:
[todsah@jib]~$ whatis du
du (1) - estimate file space usage
[todsah@jib]~$ du -hs *
93M Mail
32M Trash
426M bin
108M dev
357M download
1.8M notes
4.0K temp
And though it's not a CLI tool, XDU is still very handy. It shows a graphical representation of the output of the 'du' command:
<a href="http://sd.wareonearth.com/~phil/xdu/" title="wareonearth.com">http://sd.wareonearth.com/~phil/xdu/</a wareonearth.com>
If you like XDU, you'll love Filelight!
Requires KDE libraries.
<a href="http://www.methylblue.com/filelight/" title="methylblue.com">http://www.methylblue.com/filelight/</a methylblue.com>
Requires KDE libraries.
<a href="http://www.methylblue.com/filelight/" title="methylblue.com">http://www.methylblue.com/filelight/</a methylblue.com>
I like to use "which" inside of backticks. Some programs require the full path to a file in order to work; for example:
~$ file grep
grep: can't stat `grep' (No such file or directory).
But if I use which inside of backticks it works fine:
~$ file `which grep`<nobr> <wbr></nobr>/bin/grep: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), stripped
I also sometimes forget the name of some program but can remember part of it such as a lot of programs will have "conf" in them somewhere. If I want to see all of the programs that have "conf" in them I use:
~$ locate conf | grep bin/
And it gives me all of the programs that have "conf" in their names that are in the<nobr> <wbr></nobr>/bin<nobr> <wbr></nobr>/sbin<nobr> <wbr></nobr>/usr/bin<nobr> <wbr></nobr>/usr/sbin directories.
Cheers,
netcat
~$ file grep
grep: can't stat `grep' (No such file or directory).
But if I use which inside of backticks it works fine:
~$ file `which grep`<nobr> <wbr></nobr>/bin/grep: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), stripped
I also sometimes forget the name of some program but can remember part of it such as a lot of programs will have "conf" in them somewhere. If I want to see all of the programs that have "conf" in them I use:
~$ locate conf | grep bin/
And it gives me all of the programs that have "conf" in their names that are in the<nobr> <wbr></nobr>/bin<nobr> <wbr></nobr>/sbin<nobr> <wbr></nobr>/usr/bin<nobr> <wbr></nobr>/usr/sbin directories.
Cheers,
netcat
If you're looking for unix commands, try <a href="http://www.coolcommands.com/" title="coolcommands.com">http://www.coolcommands.com/</a coolcommands.com>
Backticks are deprecated. Use $(command) instead of `command`.
missing in action
Posted by: Anonymous Coward on July 25, 2005 05:39 PM#