Linux命令cat运用讲解lianxi.doc

Linux命令cat运用讲解Linux命令cat - concatenate files and print on the standard output把文件连接后输出到屏幕上，其实就是查看文件内容。 你们知道什么是Linux命令么这个非常高深的运用技术将由我来非常讲解，Linux命令NB在哪呢，下面我来进入讲述Linux命令的无限领域。Linux命令cat - concatenate files and print on the standard output把文件连接后输出到屏幕上，其实就是查看文件内容。SYNOPSIScat OPTION FILEDESCRIPTIONConcatenate FILE(s), or standard input, to standard output.-A,show-allequivalent to -vET -等同与参数-vET-b,number-nonblanknumber nonblank output lines -对空白行不编号，与-n有相似。-e,equivalent to -vE -等同与参数-vE-E,show-ends display $ at end of each line -每行以$符号为行结尾-n,number number all output lines -由1开始对所有输出的行数编号-s,squeeze-blank never more than one single blank line -当遇到连续2行以上的空白行，只保留一行空白行-t,equivalent to -vT-T,show-tabsdisplay TAB characters as I-u,(ignored)-v,show-nonprintinguse and M- notation, except for LFD and TABLinux命令练习：rootCentOS4 ok_008# cat mytestHello world!Hello world 1Hello world 2hello world 3rootCentOS4 ok_008# cat -n mytestHello world!Hello world 1Hello world 2hello world 3rootCentOS4 ok_008# cat -b mytest1Hello world!2Hello world 13Hello world 24hello world 3从以上Linux命令 我们可以验证 -n与 -b的差异。rootCentOS4 ok_008# cat -b -E mytest1Hello world!$2Hello world 1$3Hello world 2$4hello world 3$每行以$符号为行结尾现在想合并mytest和oktest两个文件的内容成一个新的文件NewTest.txtrootCentOS4 ok_008# ls -ltotal 24-rw-r-r- 1 root root 59 Sep 18 19:48 mytestdrwxr-xr-x 3 root root 4096 Sep 13 22:51 ok-rw-r-r- 1 root root 21 Sep 17 20:45 oktestrootCentOS4 ok_008# cat mytest oktest newtest.txtrootCentOS4 ok_008# ls -ltotal 32-rw-r-r- 1 root root 59 Sep 18 19:48 mytest-rw-r-r- 1 root root 80 Sep 18 19:53 newtest.txtdrwxr-xr-x 3 root root 4096 Sep 13 22:51 ok-rw-r-r- 1 root root 21 Sep 17 20:45 oktest查看新的文件newtest.txt的内容：rootCentOS4 ok_008# cat -b newtest.txt1 Hello world!2 Hello world 13 Hello world 24 hello world 35 this is a test file.合并两个文件的内容rootCentOS4 ok_008# cat mytest oktest newtest1.txtrootCentOS4 ok_008# ls -ltotal 40-rw-r-r- 1 root root 59 Sep 18 19:48 mytest-rw-r-r- 1 root root 80 Sep 18 19:56 newtest1.txt-rw-r-r- 1 root root 80 Sep 18 19:53 newtest.txtdrwxr-xr-x 3 root root 4096 Sep 13 22:51 ok-rw-r-r- 1 root root 21 Sep 17 20:45 oktestrootCentOS4 ok_008# cat -b newtest1.txt1 Hello world!2 Hello world 13 Hello world 24 hello world 35 this is a test file.我们仔细会发现cat mytest oktest newtest1.txt 和 cat mytest oktest newtest.txt 返回的结果在这里相同。其实根据Linux常用命令 全集的例子：cat -n textfile1 textfile2 把 textfile1 的档案内容加上行号后输入 textfile2 这个档案里cat -b textfile1 textfile2 textfile3 把 textfile1 和 textfile2 的档案内容加上行号(空白行不加)之后将内容附可以看出两个Linux命令 的差异，这里就不多写例子。Linux命令清空某个文件的内容：rootCentOS4 ok_008# cat /dev/null mytestrootCentOS4 ok_008# cat -b mytestrootCentOS4 ok_008# ls -ltotal 52-rw-r-r- 1 root root 0 Sep 18 20:05 mytest-rw-r-r- 1 root root 80 Sep 18 19:56 newtest1.txt-rw-r-r- 1 root root 93 Sep 18 20:01 newtest3.txt-rw-r-r- 1 root root 93 Sep 18 20:01 newtest4.txt-rw-r-r- 1 root root 80 Sep 18 19:53 newtest.txtdrwxr-xr-x 3 root root 4096 Sep 13 22:51 ok-rw-r-r- 1 root root 34 Sep 18 20:00 oktestLinux命令创建一个新的文件：rootCentOS4 ok_008# cat new.txt -按 CTRL + C 结束录入rootCentOS4 ok_008# ls -ltotal 56-rw-r-r- 1 root root 0 Sep 18 20:05 mytest-rw-r-r- 1 root root 80 Sep 18 19:56 newtest1.txt-rw-r-r- 1 root root 93 Sep 18 20:01 newtest3.txt-rw-r-r- 1 root root 93 Sep 18 20:01 newtest4.txt-rw-r-r- 1 root root 80 Sep 18 19:53 newtest.txt-rw-r-r- 1 root root 0 Sep 18 20:07 new.txtdrwxr-xr-x 3 root root 4096 Sep 13 22:51 ok-rw-r-r- 1 root root 34 Sep 18 20:00 oktestLinux命令温习以前的rmLinux命令 把一些刚才临时建立的文件(如newtest1.txt,newtest3.txt,newtest4.txt,newtest.txt,new.txt)删除掉：rootCentOS4 ok_008# rm newtest1.txt newttest3.txt newtest4.txt newtest.txtrm: remove regular file newtest1.txt? yrm: cannot lstat newttest3.txt: No such file or directoryrm: remove regular file newtest4.txt? yrm: remove regular file newtest.txt? yrootCentOS4 ok_008# rm newtest3.txtrm: remove regular file newtest3.txt? yrootCentOS4 ok_008# ls -ltotal 24-rw-r-r- 1 root root 0 Sep 18 20:05 mytest-rw-r-r- 1 root root 0 Sep 18 20:07 new.txtdrwxr-xr-x 3 root root 4096 Sep 13 22:51 ok-rw-r-r- 1 root root 34 Sep 18 20:00 oktestrootCentOS4 ok_008# rm newt.txtrm: cannot lstat newt.txt: No such file or directoryrootCentOS4 ok_008# rm new.