linux 命令学习1

Posted 2021-02-06

 tr命令

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.

       -c, -C, --complement
              use the complement of SET1

       -d, --delete
              delete characters in SET1, do not translate

       -s, --squeeze-repeats
              replace each sequence of a repeated character that is listed  in
              the last specified SET, with a single occurrence of that character
   

       -t, --truncate-set1
              first truncate SET1 to length of SET2

       --help display this help and exit

       --version
              output version information and exit

       SETs are specified as strings  of  characters.   Most  represent  themselves.
  Interpreted sequences are:

       \\NNN   character with octal value NNN (1 to 3 octal digits)

       \\\\     backslash

       \\a     audible BEL

       \\b     backspace

       \\f     form feed

       \\n     new line

       \\r     return

       \\t     horizontal tab

       \\v     vertical tab
eg：将 从标准输入的字符把 a替换成b 重定向到cmdlist.txt 文件中（Ctrl+z 停止输入字符）

任务： 分别计算上述命令的MAN文档的行数

         STEP1:  将上述命令放置到一个文本文件中， 命令为 cmds.list  

ls, cp, rm , mv,  cat , head, tail ,  cd ,  pwd, mkdir ,  touch,  rename,  less,  find, which, locate,  chmod, chown, less, ln,  tar,  umask
 grep, sed, awk, tr,  uniq,  sort,  join,  cut,  tee,  wc, 
ps,  top,  fg,  kill,   who,  
netstat ,  scp ,   ssh,  ping,   wget
set,  alias, . ,  source, sudo ,  su,  date, 
 man ,
xargs  

          STEP2：使用 tr 命令先将 ,  转化为 换行，并去掉空格和空行; 

             $ tr \',\' \'\\n\' < cmds.list | tr -d \' \' | grep -v \'^$\' > result.mid

           (grep -v \'^$\'意思是取非空行的行，\'^$’为正则表达式)

       step3及实验结果待续

参考：开发人员的 Linux 命令学习清单