重定向和管道

$ cat /etc/fstab > ./s
$ ls
readme.txt  s  test.bed
$ cat s
/dev/vda1            /                    ext3       noatime,acl,user_xattr 1 1
proc                 /proc                proc       defaults              0 0
sysfs                /sys                 sysfs      noauto                0 0
debugfs              /sys/kernel/debug    debugfs    noauto                0 0
devpts               /dev/pts             devpts     mode=0620,gid=5       0 0
/dev/vdb1 /public ext3 defaults 0 0
/dev/vdc /home ext3 defaults 0 0
#/dev/vdf /trainee ext3 defaults 0 0
/mnt/10GiB.swap swap swap defaults 0 0

>：覆盖输出
>>：追加输出

$ cat /etc/passwd >> ./s
$ cat s
/dev/vda1            /                    ext3       noatime,acl,user_xattr 1 1
proc                 /proc                proc       defaults              0 0
sysfs                /sys                 sysfs      noauto                0 0
debugfs              /sys/kernel/debug    debugfs    noauto                0 0
devpts               /dev/pts             devpts     mode=0620,gid=5       0 0
/dev/vdb1 /public ext3 defaults 0 0
/dev/vdc /home ext3 defaults 0 0
#/dev/vdf /trainee ext3 defaults 0 0
/mnt/10GiB.swap swap swap defaults 0 0
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin

管道
前一个命令输出，作为后一个命令的输入
命令1 | 命令2 | 命令3
$ cut -d: -f1 /etc/passwd | sort -n | tr 'a-z' 'A-Z'
AMLIANG
_APT
BACKUP
BIN
DAEMON
DBJIANG
DNSMASQ
DWANG
DZHANG
$ cut -d: -f7 /etc/passwd | sort -u

/bin/bash
/bin/false
/bin/sync
/usr/sbin/nologin

$ head -4 readme.txt  #取最后一行
Welcome to Biotrainee() !
This is your personal account in our Cloud. 
Have a fun with it.
Please feel free to contact with me( email to jmzeng1314@163.com )
$ head -4 readme.txt | tail -1
Please feel free to contact with me( email to jmzeng1314@163.com )



$ tail -9 /etc/passwd | head -1 | cut -d: -f1,7 | tee ./s #保存并显示 tee
s7:
$ ls
readme.txt  s
$ cat s
s7:


$ ls -d /etc/pa* | wc -l
5