Some computer tips

to print screen of a program:
make a small terminal - import screen.jpg - click on the program.

computer can be shut off power while hibernate state.

ps x
kill -9 20034  // kill -9 forces to kill. kill is just try to kill nicely.


To copy symbolic links:
cp -d

vi search
/p.*.root ->

replace stuffs beginning with lrwx and ending with "root -> "
with "ln -s".
:%s/lrwx.*.root -> /ln -s /gc

ls -gok

check how many files/folders inside a folder.
ls EqTwoJet/ | wc -l

landshark-clued0:~/web_area> ln -s top_write /prj_root/2671/top_write/weigang
landshark-clued0:~/web_area> mkdir d0_private

firfox enable backspace:
about:config --> find "browser.backspace_action" --> change 2 to 0.

in c++, arcsine is asin();

at fermilab, the print command is "kprinter"
actually most of the time it doesn't work. so
1. print page to file "xx.pdf";
2. print pdf.
most of the time this way it's successful.

in term command line,
^a to the beginning
^e to the end.

To edit wiki, just click on "edit", not the pen.

list principles:
> klist

kill sam many jobs:
for i in `seq -f %8.0f 3894489 3894584`; do echo $i; qdel $i.d0cabsrv1.fnal.gov; sleep 1; done

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to subscribe a fermilab mailist:

    from    my email
    to    listserv@fnal.gov
    subject    Subscribe fermiultimate
  
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Wait 3 hours then play foo.mp3 :

sleep 3h ; mplayer foo.mp3

shell 计算器:
bc or python

scp server:filename . (from server to localhost)
scp filename servername:. (from localhost to server)


accessing windows drives from linux

1. su - to become root user
2. fdisk -l to see all your hard drives and partitions;
    anything that has NTFS or FAT32 or VFAT is a windows partition. Ignore Windows 95 Ext'd; they are not really a data partition.
3. mount -t type /dev/partition /mnt (or /media)
e.g.
    cd /media
    mkdir system
    mount -t ntfs /dev/sda1 /media/system
you can now view the contents of that drive.
    # ls /media/system/
4. when you are finished with the drive,
    umount /mnt

* note to be able to do step 2, you need to have all packages starting with ntfs installed.

env Lists your current environment variables and their settings:
$ whatis env
env (1)              - run a program in a modified environment


use alias to list command shortcuts:

$ alias
$ eject


$ pstree

 1191  tar -cvf pythia8135_new.tar pythia8135_new/
 1194  gzip pythia8135_new.tar

1196  scp pythia8135_new.tar.gz weigang@landshark-clued0.fnal.gov:/work/landshark-clued0/weigang

nan = not a number

to show Chinese characters:
gedit --encoding=gbk .fcitx/config


gcc is located at directory /usr/bin/gcc

$ gcc -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.4.1-4ubuntu9' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --program-suffix=-4.4 --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-targets=all --disable-werror --with-arch-32=i486 --with-tune=generic --enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9)


ps -ef | less
ps aux | less

the length of array should use const.


make all files under a folder readable to everyone:
landshark-clued0:/d0mino> chmod +r weigang -R

to list only hidden files:
ls -a | grep '^\.'

lp -d d0tcn_hp8150_d
lpq

klist -f
qstat -u weigang @d0cabsrv1

cat *.lst | sort | uniq
# merges and sorts all ".lst" files, then deletes duplicate lines.

the "if-grep" construct:

if grep -q Bash file
 then echo "File contains at least one occurrence of Bash."
fi

The "if COMMAND" construct returns the exit status of COMMAND.

These 3 are equivalent:

if [ $condition1 ] && [ $condition2 ]
if [ $condition1 -a $condition2 ]
if [[ $condition1 && $condition2 ]]

echo $MACHTYPE $OSTYPE $PS1 $PS2 $PROMPT_COMMAND $TERM $SHELL

$PATH: Path to binaries, /usr/bin/, /usr/local/bin/, etc.
may store in ~/.bashrc. 

cat /proc/cpuinfo

$ str=adasdf
$ echo ${#str}

Remove blank lines using grep
$ grep -v '^$' input.txt > output.txt