bash 如何使用 cat 读取文件的第一行？
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How do I read the first line of a file using cat?
提问by Doboy
How do I read the first line of a file using cat?
如何使用 读取文件的第一行cat？
回答by Carl Norum
You don't need cat.
你不需要cat.
head -1 file
will work fine.
会正常工作。
回答by Orbling
You don't, use headinstead.
你不要，head改用。
head -n 1 file.txt
回答by JJJ
There are many different ways:
有很多不同的方式：
sed -n 1p file
head -n 1 file
awk 'NR==1' file
回答by Mike Pelley
You could use cat file.txt | head -1, but it would probably be better to use head directly, as in head -1 file.txt.
您可以使用cat file.txt | head -1，但直接使用 head 可能会更好，如head -1 file.txt.
回答by mwcz
This may not be possible with cat. Is there a reason you have to use cat?
使用cat. 你有理由使用cat吗？
If you simply need to do it with a bash command, this should work for you:
如果您只需要使用 bash 命令执行此操作，这应该适合您：
head -n 1 file.txt
回答by josh.trow
catalone may not be possible, but if you don't want to use headthis works:
cat单独可能是不可能的，但如果你不想使用head这个作品：
cat <file> | awk 'NR == 1'
回答by Charles Duffy
I'm surprised that this question has been around as long as it has, and nobody has provided the pre-mapfile built-in approach yet.
我很惊讶这个问题一直存在，而且还没有人提供 pre-mapfile 内置方法。
IFS= read -r first_line <file
...puts the first line of the file in the variable expanded by "$first_line", easy as that.
...将文件的第一行放在由 展开的变量中"$first_line"，就这么简单。
Moreover, because readis built into bash and this usage requires no subshell, it's significantly more efficient than approaches involving subprocesses such as heador awk.
此外，由于read内置于 bash 中，并且这种用法不需要子 shell，因此它比涉及子进程的方法（如head或 ）要高效得多awk。
回答by jm666
You dont need any external command if you have bash v4+
如果您有 bash v4+，则不需要任何外部命令
< file.txt mapfile -n1 && echo ${MAPFILE[0]}
or if you really want cat
或者如果你真的想要 cat
cat file.txt | mapfile -n1 && echo ${MAPFILE[0]}
:)
:)
回答by Praveenkumar Sekar
Use the below command to get the first row from a CSV file or any file formats.
使用以下命令从 CSV 文件或任何文件格式中获取第一行。
head -1 FileName.csv
