linux命令管道符"|"和重定向

管道符   
    利用Linux所提供的管道符“|”将两个命令隔开，管道符左边命令的输出就会作为管道符右边命令的输入。连续使用管道意味着第一个命令的输出会作为第二个命令的输入，第二个命令的输出又会作为第三个命令的输入，依此类推。下面来看看管道是如何在构造一条Linux命令中得到应用的。

[developer@app02v /data/html/m.expai.com]$ ps -ax|grep api
Warning: bad syntax, perhaps a bogus '-'? See /usr/share/doc/procps-3.2.8/FAQ
13676 ?        Sl    10:14 java -classpath /data/html/api.expai.com/lib/*:/data/html/api.expai.com/conf/ com.expai.server.APIServer
31779 pts/1    S+     0:00 grep api

重定向
> 将stdout(标准输出)重定向到文件(覆盖)

[duming@app01v /data]$ ll > outfile
[duming@app01v /data]$ ll
؜ԃ 20
drwxrwxrwx 2 developer developer 4096 12Ղ  6 2013 backup
drwxrwxr-x 3 duming    duming    4096  1Ղ 16 2014 htdocs
drwxrwxrwx 9 developer developer 4096  8Ղ  6 13:34 html
drwxrwxrwx 9 developer developer 4096  7Ղ 31 18:32 logs
-rw-rw-r-- 1 duming    duming     300  8Ղ 10 23:20 outfile
[duming@app01v /data]$ cat outfile
؜ԃ 16
drwxrwxrwx 2 developer developer 4096 12Ղ  6 2013 backup
drwxrwxr-x 3 duming    duming    4096  1Ղ 16 2014 htdocs
drwxrwxrwx 9 developer developer 4096  8Ղ  6 13:34 html
drwxrwxrwx 9 developer developer 4096  7Ղ 31 18:32 logs
-rw-rw-r-- 1 duming    duming       0  8Ղ 10 23:20 outfile
[duming@app01v /data]$ 

>>将stdout(标准输出)重定向到文件(追加)

[duming@app01v /data/html]$ ll >> /data/outfile 
[duming@app01v /data/html]$ cat /data/outfile 
؜ԃ 16
drwxrwxrwx 2 developer developer 4096 12Ղ  6 2013 backup
drwxrwxr-x 3 duming    duming    4096  1Ղ 16 2014 htdocs
drwxrwxrwx 9 developer developer 4096  8Ղ  6 13:34 html
drwxrwxrwx 9 developer developer 4096  7Ղ 31 18:32 logs
-rw-rw-r-- 1 duming    duming       0  8Ղ 10 23:20 outfile
؜ԃ 28
drwxrwxrwx 6 developer developer 4096  7Ղ 23 16:44 api.expai.com
drwxrwxrwx 9 developer developer 4096 12Ղ 20 2013 m.expai.com
drwxrwxrwx 4 developer developer 4096 10Ղ 24 2013 mongo.expai.com
drwxrwxrwx 5 developer developer 4096  1Ղ 10 2014 r.expai.com
drwxrwxr-x 7 developer developer 4096  7Ղ 31 17:59 searchimg.expai.com
drwxrwxrwx 2 developer developer 4096  1Ղ 17 2014 shibin
drwxrwxrwx 5 developer developer 4096 12Ղ  4 2013 spider.expai.com
[duming@app01v /data/html]$ 

2>讲stderr(标准错误)重定向到文件(覆盖)

[duming@app01v /data/html]$ ll www.baidu.com
ls: Ϟ·¨·Ďɷww.baidu.com: ûԐҸþ»倂¼
[duming@app01v /data/html]$ ll www.baidu.com 2>/data/outfile 
[duming@app01v /data/html]$ cat /data/outfile 
ls: Ϟ·¨·Ďɷww.baidu.com: ûԐҸþ»倂¼
[duming@app01v /data/html]$ 

2>&1讲stderr(标准错误)和stdout(标准输出)结合
<重定向stdin(标准输入) grep linux < /etc/passwd (在passd文件中找linux关键字)