Linux 如何使用 Bash 读取文件中的倒数第二行？
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How to read the second-to-last line in a file using Bash?
提问by World
I have a file that has the following as the last three lines. I want to retrieve the penultimate line, i.e. 100.000;8438; 06:46:12.
我有一个文件的最后三行如下。我想检索倒数第二行，即100.000;8438; 06:46:12.
.
.
.
99.900; 8423; 06:44:41
100.000;8438; 06:46:12
Number of patterns: 8438
I don't know the line number. How can I retrieve it using a shell script? Thanks in advance for your help.
我不知道行号。如何使用 shell 脚本检索它？在此先感谢您的帮助。
采纳答案by MattH
Try this:
尝试这个：
tail -2 yourfile | head -1
回答by S B
Use this
用这个
tail -2 <filename> | head -1
回答by janc
edand sedcan do it as well.
ed并且sed也可以做到。
str='
99.900; 8423; 06:44:41
100.000;8438; 06:46:12
Number of patterns: 8438
'
printf '%s' "$str" | sed -n -e '${x;1!p;};h' # print last line but one
printf '%s\n' H '$-1p' q | ed -s <(printf '%s' "$str") # same
printf '%s\n' H '$-2,$-1p' q | ed -s <(printf '%s' "$str") # print last line but two
回答by Dario More Escamez
To clarify what has already been said:
澄清已经说过的内容：
ec2thisandthat | sort -k 5 | grep 2012- | awk '{print }' | tail -2 | head -1
snap-e8317883
snap-9c7227f7
snap-5402553f
snap-3e7b2c55
snap-246b3c4f
snap-546a3d3f
snap-2ad48241
snap-d00150bb
returns
返回
snap-2ad48241
回答by Chen Levy
From: Useful sed one-linersby Eric Pement
来自：Eric Pement 的有用 sed one-liners
# print the next-to-the-last line of a file
sed -e '$!{h;d;}' -e x # for 1-line files, print blank line
sed -e '1{$q;}' -e '$!{h;d;}' -e x # for 1-line files, print the line
sed -e '1{$d;}' -e '$!{h;d;}' -e x # for 1-line files, print nothing
You don't need all of them, just pick one.
您不需要所有这些，只需选择一个即可。
回答by plhn
tac <file> | sed -n '2p'
回答by paranoidduck
A short sed one-liner inspired by https://stackoverflow.com/a/7671772/5287901
受https://stackoverflow.com/a/7671772/5287901启发的简短 sed one-liner
sed -n 'x;$p'
Explanation:
解释：
-nquiet mode: dont automatically print the pattern spacex: exchange the pattern space and the hold space (hold space now store the current line, and pattern space the previous line, if any)$: on the last line,p: print the pattern space (the previous line, which in this case is the penultimate line).
-n安静模式：不自动打印模式空间x: 交换模式空间和保持空间（保持空间现在存储当前行，模式空间存储前一行，如果有的话）$: 在最后一行，p: 打印模式空间（前一行，在本例中是倒数第二行）。
