如何使用grep取得一行中的一部分

Question

当我尝试发送ifconfig命令即时得到这个

ath0  IEEE 802.11ng  ESSID:"test"  Nickname:""
      Mode:Master  Frequency:2.412 GHz  Access Point: 00:00:00:00:00:00
      Bit Rate:0 kb/s   Tx-Power=-4 dBm   Sensitivity=16/16
      Retry:off   RTS thr:off   Fragment thr:off
      Encryption key:off
      Power Management:off
      Link Quality=0/94  Signal level=-96 dBm  Noise level=-96 dBm
      Rx invalid nwid:475654423  Rx invalid crypt:0  Rx invalid frag:0
      Tx excessive retries:0  Invalid misc:0   Missed beacon:0

如何从例如行这只是部分得到

ESSID:""test
Frequency:2.412 GHz

Answer 1

鉴于您的实际糊（和忽视畸形样本输出）：

$ cat ifconf 
ath0  IEEE 802.11ng  ESSID:"test"  Nickname:""
      Mode:Master  Frequency:2.412 GHz  Access Point: 00:00:00:00:00:00
      Bit Rate:0 kb/s   Tx-Power=-4 dBm   Sensitivity=16/16
      Retry:off   RTS thr:off   Fragment thr:off
      Encryption key:off
      Power Management:off
      Link Quality=0/94  Signal level=-96 dBm  Noise level=-96 dBm
      Rx invalid nwid:475654423  Rx invalid crypt:0  Rx invalid frag:0
      Tx excessive retries:0  Invalid misc:0   Missed beacon:0
$ grep -oE 'ESSID:"[^"]+"|Frequency:[^ ]+' ifconf
ESSID:"test"
Frequency:2.412

它实际上只是一个扩展的正则表达式，和grep的-o标志，只输出精确匹配，而不是匹配的行。