Home - Linux

For notes on Solaris/SunOS, this way.

this page is a random collection of things related to shell, C compiling, and etc:

HTML Colors

http://www.computerhope.com/htmcolor.htm

ssh-agent

after running, copy the output and run them:

SSH_AUTH_SOCK=/tmp/ssh-ABIxF27536/agent.27536; export SSH_AUTH_SOCK;
SSH_AGENT_PID=27537; export SSH_AGENT_PID;
echo Agent pid 27537;

then use ssh-add to add keys.

ssh-add -l will list keys on the agent

more references

get cpu information

in file /proc/cpuinfo

screen

screen is a powerful tool for text-mode operation. The most useful feature is that you even your terminal dies, your program can still be running in screen.

there's little information on the official page. But the man page and info page look good.

this link is good to start with: http://www.kuro5hin.org/story/2004/3/9/16838/14935

To change escape character, edit .screenrc, e.g.

escape ^Vv

patch for GNU screen: added vertical split http://fungi.yuggoth.org/vsp4s/

In bash, set screen title to current running program, with this in .bashrc

export PS1="[\u@\h \w]"'\033k\033\\\$ '

Then in .screenrc

shelltitle "$ |bash"

In tcsh, add this in .cshrc

if ($TERM == 'screen') then
  alias postcmd 'echo -n "\ek${USER}@${HOST}:${cwd} - `history -h 1`\e\\"'
endif

Another example to start multiple ssh in .screenrc

escape ^Vv
vbell on
autodetach on
startup_message off
defscrollback 2048

hardstatus alwayslastline "%{= kK}%50>%n%f %< %{=kG}%-= %M %d %c:%s"

sessionname box
screen ssh ccjbox5
stuff "cd /ccj/w/data05z/run8pp-ndst/run8-agg\015\015"
screen ssh ccjbox6
stuff "cd /ccj/w/data06z/run8pp-ndst/run8-agg\015\015"
screen ssh ccjbox7
stuff "cd /ccj/w/data07z/run8pp-ndst/run8-agg\015\015"
screen ssh ccjbox8
stuff "cd /ccj/w/data08z/run8pp-ndst/run8-agg\015\015"

if it's in a file other than .screenrc, can be run with "screen -c [filename]"

make, Makefile, automake, autoconf, etc.

My notes are here.

Shell

/usr/bin/sh -n will check the syntax

use set -x to print out something, set +x will change it back.

be careful about spaces around = and anywhere else in the script

Libraries

Check if libs are linked correctly

ldd [your program]

Calling the libs dynamically is to use dlopen(), dlsym(), dlclose() and etc. Find some examples here.

redirection

an example

[yangrz@rcas2070 ~]$ root -b <<EOF
? .ls
? .q
?   *******************************************
  *                                         *
  *        W E L C O M E  to  R O O T       *
  *                                         *
  *   Version   4.01/02   9 February 2006   *
  *                                         *
  *  You are welcome to visit our Web site  *
  *          http://root.cern.ch            *
  *                                         *
  *******************************************

Compiled for linux with thread support.

CINT/ROOT C/C++ Interpreter version 5.15.152, Sep 13 2004
Type ? for help. Commands must be C++ statements.
Enclose multiple statements between { }.
TROOT*          Rint    The ROOT of EVERYTHING
[yangrz@rcas2070 ~]$

Find printers

look at /etc/printcap, then use "lpr -Pprintername filename"

AFS & quota

the AFS cell for rhic is called "rhic".

klog kerbos login
unlog destroy tokens
tokens list tokens
fs lq: see quota for afs
quota -v: see quota
fs listacl filename: access

Find

this part is copied from BABAR work book To find a file, use the command:

   > find start_directory -name filename -print

This will initiate a search through the directory start_directory and all its subdirectories, for the file filename. Wildcards may be used in the filename, but in this case, the filename must be quoted. Examples:

   > find . -name myfile.txt -print
   > find .. -name "*.txt" -print

You may wish to put an alias in your .cshrc file to handle the simplest use of this command:

   > alias findfile "find . -name \!^ -print"

Find file size greater than 1G

find -name '*' -size +1000k

Find file modified in last 30 min

find . -mmin -30

Run multiple commands

find *tar -exec sh -c "tar xvf {}; rm {}" \;

More examples http://www.linux.ie/newusers/beginners-linux-guide/find.php

Disk Usage

sort the disk usage without the annoying error message:

du -s * 2>/dev/null | sort -n

-h for du will display size in K, M, G, ...

create dirs named by numbers

mkdir `seq -s " " 1 20`

go back

cd -

dealing with processes

fg, bg, jobs, stop, kill, top, etc. kill something by number instead of PID e.g. kill %5. The number can be seen using jobs.

look at files

cat, more, head, tail, diff and etc.

cat -n print file with line numbers.

tail -20 filename prints last 20 lines.

grep is very powerful command, it is usually used with pipes. It can also be used to find string in a file like: grep "some string" filename.

Note that grep looks for regexp while fgrep looks for literal string.

sometimes sdiff is preferred than diff, e.g. use sdiff liek this sdiff -w40 file1 file2

mount USB

cd /mnt/
su
mkdir usbflash
mount /dev/sda1 /mnt/usbflash
ls usbflash
umount /dev/sda1 /mnt/usbflash

UIUC specific information

ph server: ns.uiuc.edu

nntp server: news.ks.uiuc.edu

UIUC CITES services

top

show 1 screen and exit

top -b -n1

Free X server under Windows

Xming : http://www.straightrunning.com/XmingNotes/

Screen capture

import from ImageMagick package

to get the id of an X window, use xwininfo

TightVNC

include both server and viewer, works well under Windows XP and Unbuntu Linux

definition of load average in UNIX/Linux

http://www.teamquest.com/resources/gunther/display/5/

const and C++

http://duramecho.com/ComputerInformation/WhyHowCppConst.html

webcron

cron from their website:

http://www.webcron.org/index.php?&lang=en

The UNIX-haters' Handbook

web.mit.edu/~simsong/www/ugh.pdf

run at boot

The easy way, put it in /etc/rc.local

or write a script that conforms to the rules as in the policy of the specific distribution.

Then update the rc.d scripts. For example, in Debian/Ubuntu:

update-rc.d php-fpm defaults

Integer types with exact bits

http://www.nongnu.org/avr-libc/user-manual/group__avr__stdint.html

csh and rsh

from rsh's man page:

       If you are using csh(1) and put a rsh(1) in the background without redirecting its input away  from  the
       terminal,  it  will block even if no reads are posted by the remote command.  If no input is desired you
       should redirect the input of rsh to /dev/null using the -n option.

       You cannot run an interactive command (like rogue(6) or vi(1)); use rlogin(1).

       Stop signals stop the local rsh process only; this is arguably wrong, but currently hard to fix for rea-
       sons too complicated to explain here.

less

to preserve the ANSI colors, use -R option

ANSI codes: http://www.dee.ufcg.edu.br/~rrbrandt/tools/ansi.html

redirect stderr separately in csh

yeah we all hate csh, let sh do it for you

sh -c 'command 1>out.txt 2>err.txt &'

the csh way is an abomination

( command >stdout_file ) >&stderr_file

exact width integers

http://en.wikipedia.org/wiki/Stdint.h

portability notes

http://cr.yp.to/docs/unixport.html

ImageMagick

print image size, etc:

identify <file>

convert -size 1869x672 xc:black all.png
composite -gravity northwest 2A.png all.png all.png
composite -gravity north     2B.png all.png all.png
composite -gravity northeast 2C.png all.png all.png
composite -gravity southwest 3A.png all.png all.png
composite -gravity south     3B.png all.png all.png
composite -gravity southeast 3C.png all.png all.png