Linux/Unix tr、变量、运算以及终端特性的设置等

Linux/Unix tr、变量、运算以及终端特性的设置等

使用tr的-s选项去除重复出现的字符：

[oracle@localhost tr.folder]$ cat oops.txt

And the cowwwwwws went homeeeee

Or did theyyyyyyyyyyyyy

[oracle@localhost tr.folder]$ tr -s "[a-z]" < oops.txt

And the cows went home

Or did they

删除空行：

[oracle@localhost tr.folder]$ cat oops.txt

And the cowwwwwws went homeeeee

Or did theyyyyyyyyyyyyy

fas ods css

[oracle@localhost tr.folder]$ tr -s "[\012]" < oops.txt

And the cowwwwwws went homeeeee

Or did theyyyyyyyyyyyyy

fas ods css

转换大小写：

[oracle@localhost tr.folder]$ echo "hello today is a Fine DAY" | tr "[a-z]" "[A-Z]"

HELLO TODAY IS A FINE DAY

删除数字：

[oracle@localhost tr.folder]$ cat oops.txt

And the cowwwwwws went homeeeee

23

3123asadfas

123ffff

Or did theyyyyyyyyyyyyy

12

fas ods css

[oracle@localhost tr.folder]$ tr -cs "[a-z][A-Z]" "[\012*]" < oops.txt

And

the

cowwwwwws

went

homeeeee

asadfas

ffff

Or

did

theyyyyyyyyyyyyy

fas

ods

css

[oracle@localhost etc]$ echo "`who | wc -l` users are on today"

2 users are on today

查看当前终端特性：

[oracle@localhost testDir]$ stty -a

speed 38400 baud; rows 44; columns 167; line = 0;

intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ; eol2 = ; swtch = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W;

lnext = ^V; flush = ^O; min = 1; time = 0;

-parenb -parodd cs8 -hupcl -cstopb cread -clocal -crtscts

-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany -imaxbel -iutf8

opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0

isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke

设置styy xxx "xxx"

设置变量的默认值：

[oracle@localhost testDir]$ day=bad

[oracle@localhost testDir]$ echo "today is a ${day:-fine} day"

today is a bad day

[oracle@localhost testDir]$ unset day

[oracle@localhost testDir]$ echo "today is a ${day:-fine} day"

today is a fine day

设置只读变量：

[oracle@localhost testDir]$ readonly

declare -ar BASH_VERSINFO='([0]="3" [1]="1" [2]="17" [3]="1" [4]="release" [5]="i686-redhat-linux-gnu")'

declare -ir EUID="501"

declare -ir PPID="19022"

declare -r SHELLOPTS="braceexpand:emacs:hashall:histexpand:history:interactive-comments:monitor"

declare -ir UID="501"

[oracle@localhost testDir]$ weather=fine

[oracle@localhost testDir]$ readonly weather

[oracle@localhost testDir]$ echo ${weather}

fine

[oracle@localhost testDir]$ weather=fine2

-bash: weather: readonly variable

设置环境变量：

[oracle@localhost testDir]$ console=tty1;export console

[oracle@localhost testDir]$ echo $console

tty1

显示所有环境变量：

env

设置终端类型：

[oracle@localhost testDir]$ TERM=linux;export TERM

[oracle@localhost testDir]$ echo $TERM

linux

shell中的运算：

[oracle@localhost testDir]$ var=`date +%Y%m%d`

[oracle@localhost testDir]$ let "var2=$var+1"

[oracle@localhost testDir]$ echo $var2

20130304

[oracle@localhost testDir]$ echo $((var2=$var+3))

20130306

[oracle@localhost testDir]$ echo var2=$[$var+3]

var2=20130306

[oracle@localhost testDir]$ let "var++"

[oracle@localhost testDir]$ echo $var

20130304

[oracle@localhost testDir]$ echo $[var+1]

20130305

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