shell1

shebang = sharp-bang = #!

1.echo $PATH

   export PATH="$PATH:/home/user/bin"

PREPEND

prepend() { [ -d "$2" ] && eval $1="$2':'$$1" && export $1; }

2.echo -e "e[1;31m This is red text e[0m"

0 black 30 red 31 green 32 yellow 33 bule 34 yangred 35 qing 36 white 37

backgroud color 0 black 40 red 41 green 42 y 43 bule 44 yangred 45 qing 46 white 47

3.env

cat /proc/$PID/environ

pgrep gedit  -> serch process ID

4.let (()) [  ]   bc

echo "scale=2;22/7" | bc

5.$?

echo $?

6. command | tee FILE1 FILE2  | otherCommand

cat a* | tee -a out.txt | cat -n     # -a  add

7.declare -A ass_array

8.alias rm='cp $@ ~/backup && rm $@'

unalias

command 

&& yu

||  huo

-eq =

-ne  !

-gt >

-lt <

-ge >=

-le <=

9. if condition;

then

commands;

fi

if conditon;

then

commands;

else if condition; then

commands;

else

commands;

fi

10.

 find

find . -type f -print

file type : f l d c b s p

-atime

-mtime

-ctime

find . -type f -atime -7 -print

-amin

-mmin

-cmin

find . -type f -amin +7 -print

-newer

find . -type f -newer file.txt -print

find . -type f -size +2k

-2k

2k

find . -type f -perm 644 -print

find . -type f -name "*.php" ! -perm 644 -print

find . -type f -user slynux -print

find . -type f -name "*.swp" -delete

find . -type f -user root -exec chown slynux { } ;

find . -type f -name '*.c' -exec cat { } ;>all_c_files.txt

find . -type f -name '*.c' -exec cat { } >all_c_files.txt ;

find . -type f -name '*.c' -exec cat { } >all_c_files.txt +

find . -type f -mtime +10 -name "*.txt" -exec cp { } OLD ;

find . -type f -name "*.txt" -exec printf "text file: %s " { } ;

11. xargs

echo "split1Xsplit2Xsplit3X" | xargs -d X

echo "splitXsplitXsplitXsplit" | xargs -d X -n 2