grep -A1 'blah' logfile
多亏了这个命令，每一行都有'blah'，我得到了包含'blah'的行输出和日志文件中的下一行。这可能是一个简单的，但我找不到一种方法来省略一行有'blah'，只显示下一行在输出。
当前回答
you can use grep, then take lines in jumps: grep -A1 'blah' logfile | awk 'NR%3==2' you can also take n lines after match, for example: seq 100 | grep -A3 .2 | awk 'NR%5==4' 15 25 35 45 55 65 75 85 95 explanation - here we want to grep all lines that are *2 and take 3 lines after it, which is *5. seq 100 | grep -A3 .2 will give you: 12 13 14 15 -- 22 23 24 25 -- ... the number in the modulo (NR%5) is the added rows by grep (here it's 3 by the flag -A3), +2 extra lines because you have current matching line and also the -- line that the grep is adding.
其他回答
使用grep可以输出行号(-n)。通过<num>:和<num>-，匹配和下一行之间的输出是不同的:
# grep -A1 -n '230 Login successful."$' /var/log/vsftpd.log
1:Sat Nov 5 03:29:43 2022 [pid 10] [foo] FTP response: Client "10.1.1.1", "230 Login successful."
2-Sat Nov 5 03:29:43 2022 [pid 10] [foo] FTP response: Client "10.1.1.1", "221 Goodbye."
3:Sat Nov 5 04:44:41 2022 [pid 10] [foo] FTP response: Client "10.1.1.1", "230 Login successful."
4-Sat Nov 5 04:44:42 2022 [pid 10] [foo] FTP response: Client "10.1.1.1", "221 Goodbye."
这样我们就可以过滤输出，只得到每个匹配的下一行:
# grep -A1 -n '230 Login successful."$' /var/log/vsftpd.log | grep -E "^[0-9]+-" | cut -d"-" -f2-
Sat Nov 5 03:29:43 2022 [pid 10] [foo] FTP response: Client "10.1.1.1", "221 Goodbye."
Sat Nov 5 04:44:42 2022 [pid 10] [foo] FTP response: Client "10.1.1.1", "221 Goodbye."
如果你想坚持使用grep:
grep -A1 'blah' logfile | grep -v "blah"
或者使用sed:
sed -n '/blah/{n;p;}' logfile
如果下一行从来没有包含'blah'，你可以过滤他们:
grep -A1 blah logfile | grep -v blah
使用cat logfile |…不需要。
你可以匹配多行，然后输出n行:
awk 'c&&!--c;/match1/{c=1};/match2/{c=2}' file
匹配多个项目，输出n行后:
#!/bin/sh
[ -z $3 ] && echo $0 file \[match n\]+... \# to output line n after match && exit
f=$1; shift; while [ \! -z $2 ]; do s="$s/$1/{c=$2};"; shift; shift; done
awk 'c&&!--c;'$s $f
所以你可以把上面的文件保存为match .sh和chmod +x match .sh，然后如果你有一个这样的文件:
line1
line2
line3
line4
line5
line6
line7
并运行:
./matchn.sh file line1 1 line3 2 line6 1
你会得到:
line2
line5
line7
这将需要更多的调整来支持0偏移量。
我不知道有什么方法可以用grep来做到这一点，但是使用awk可以达到相同的结果:
awk '/blah/ {getline;print}' < logfile
