命令——tr

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文本处理工具命令——tr

一帮助说明

TR()                                       User Commands                                       TR()

NAME
       tr - translate or delete characters

SYNOPSIS
       tr [OPTION]... SET1 [SET2]

DESCRIPTION
       Translate, squeeze, and/or delete characters from standard input, writing to standard output.

二常用选项

（一）删除字符或者分隔符

-d，--delete delete characters in SET1，do not translate删除指定字符，不做替换

-C，-C，--complement use the complement of SET1取删除指定字符的补集，相当r,reverse反转

示例——删除空白符

[root@centos73 ~]# df
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda2       52403200 1451152  50952048   3% /
devtmpfs          487964       0    487964   0% /dev
tmpfs             498988       0    498988   0% /dev/shm
tmpfs             498988   14076    484912   3% /run
tmpfs             498988       0    498988   0% /sys/fs/cgroup
/dev/sr0         4364408 4364408         0 100% /mnt
/dev/sda3       20961280   87452  20873828   1% /app
/dev/sda1        1038336  126596    911740  13% /boot
tmpfs              99800       0     99800   0% /run/user/

[root@centos73 ~]# df  |  tr   -d  ' '
Filesystem1K-blocksUsedAvailableUse%Mountedon
/dev/sda2524032001451152509520483%/
devtmpfs48796404879640%/dev
tmpfs49898804989880%/dev/shm
tmpfs498988140764849123%/run
tmpfs49898804989880%/sys/fs/cgroup
/dev/sr0436440843644080100%/mnt
/dev/sda32096128087452208738281%/app
/dev/sda1103833612659691174013%/boot
tmpfs998000998000%/run/user/

示例——使用设备生成随机数

默认显示的很多随机数是乱码的，要对其进行过滤，取出前30个没有乱码的字符

取出数字加字母就够用了

[root@centos72 ~]# cat  /dev/urandom  |  tr  -cd  '[:alnum:]' |  head  -c30
GcCS7V3zdbxf7ULACZxyileWOkVbb4[root@centos72 ~]# cat  /dev/urandom  |  tr  -dc   '[:alnum:]' |  head  -c30
4HRYAPkEmR9IU5DmwUCfPH5yFchmWk[root@centos72 ~]# cat  /dev/urandom  |  tr  -dc   '[:alnum:]' |  head  -c30
Xai5M56ExMu3lPTk3uItOrqOIyrHBi[root@centos72 ~]# cat  /dev/urandom  |  tr  -dc   '[:alnum:]' |  head  -c30
EM19jKg8elb0XaBZ5fBt6HlzvADj6V[root@centos72 ~]# cat  /dev/urandom  |  tr  -dc   '[:alnum:]' |  head  -c30
2nGHfnxibhXymvYY50933w9IKZY2a1[root@centos72 ~]# cat  /dev/urandom  |  tr  -dc   '[:alnum:]' |  head  -c30
FtlUPlUBAJqGuCF8D8mBWUA1Qy4mIE[root@centos72 ~]# cat  /dev/urandom  |  tr  -dc   '[:alnum:]' |  head  -c30
pP7Qq0iqqv3ualzDdf6JYcyA7nnL0X[root@centos72 ~]# cat  /dev/urandom  |  tr  -dc   '[:alnum:]' |  head  -c30
mcrr0qTGkAgFQ4Qp8wQYEOXkth6KBh[root@centos72 ~]# 

示例——取6个字符，包含大小写字母

[root@centos71 ~]# tr -cd  'a-zA-Z0-9'< /dev/urandom  |  head  -c6
5PWu0c[root@centos71 ~]# tr -cd  'a-zA-Z0-9'< /dev/urandom  |  head  -c6
eMHkgL[root@centos71 ~]# tr -cd  'a-zA-Z0-9'< /dev/urandom  |  head  -c6
RlO3EL[root@centos71 ~]# tr -cd  'a-zA-Z0-9'< /dev/urandom  |  head  -c6
pGlDTU[root@centos71 ~]# tr -cd  'a-zA-Z0-9'< /dev/urandom  |  head  -c6
0WI1oX[root@centos71 ~]# tr -cd  'a-zA-Z0-9'< /dev/urandom  |  head  -c6
pwho9R[root@centos71 ~]# tr -cd  'a-zA-Z0-9'< /dev/urandom  |  head  -c6
IRe8FV[root@centos71 ~]# 

（二）-s保留连续字符的第1个字符，删除其他字符

-s, --squeeze-repeats
              replace  each input sequence of a repeated character that is listed in SET1 with a sin?
              gle occurrence of that character

[root@centos73 ~]# df |grep "/sd" |tr -s  " "
/dev/sda2    % /
/dev/sda3    % /app
/dev/sda1    % /boot
[root@centos73 ~]# df  |grep "/sd"
/dev/sda2             % /
/dev/sda3               % /app
/dev/sda1                % /boot

[root@centos73 ~]# cat /etc/issue
\S
Kernel \r on an \m

[root@centos73 ~]# tr  'abcd'   'xyz'  <  /etc/issue
\S
Kernel \r on xn \m

[root@centos73 ~]# cat  /etc/issue
\S
Kernel \r on an \m

难点——tr的替换

情形一：替换前字符长度等于替换后字符长度

这种情况最简单，全部替换，并且一一对应

[root@centos71 test2]# echo  abcd  >  tr3.txt
[root@centos71 test2]# cat  tr3.txt
abcd
[root@centos71 test2]# tr  'abcd'  '1234'  <  tr3.txt

情形二：替换前字符长度大于替换后字符长度

前者多余的字符被后者最后一个字符替换

[root@centos71 test2]# echo  abcd  >>  tr.txt
[root@centos71 test2]# cat tr.txt
abcd
[root@centos71 test2]# tr  'abcd'  '123'
^C
[root@centos71 test2]# tr  'abcd'  '123'  <  tr.txt

情形三：替换前字符长度小于替换后字符长度

前者多余的字符保留

[root@centos71 test2]# echo   abcd  >  tr2.txt
[root@centos71 test2]# cat  tr2.txt
abcd
[root@centos71 test2]# tr  'abc'  '1234' <  tr2.txt
123d

情形四：替换前后字符出现重复情况

替换为最后出现的字符

[root@centos71 test2]# echo   abcba  >  tr4.txt
[root@centos71 test2]# cat  tr4.txt
abcba
[root@centos71 test2]# tr  'abcba'  '123456'  <  tr4.txt