仅当bash中存在头文件时，才如何从文件中删除头文件？

Question

I have this sample file. I want to remove the first line (header) of this file only when it (header) exist using bash.

id name job_id
1 john 25
2 adam 45
3 paul 75

Answer 1

You can do it in one operation with sed using the -i option (assuming your version of sed supports it — not all do). For example:

sed -i.bak -e '1{/^id name job_id/d;}' file

This takes line 1 of the file and applies the commands in the braces to it. The braces search for the pattern shown and delete the line. If the first line doesn't match, it isn't deleted. Other lines are left untouched.

The semicolon and backup suffix are necessary with Mac OS X sed ; with GNU sed , you could omit either or both.

Answer 2

你也可以使用awk来做到这一点：

awk 'NR!=1||$0!="id name job_id" {print $0}' file > newfile

Answer 3

filename='myfile'
[[ $(head -n 1 -- "$filename") == 'id name job_id' ]] && sed -i '1d' -- "$filename"

Answer 4

if head -1 original.txt | grep -Fxq 'id name job_id'
then tail -n+2 original.txt > newdoc.txt
fi

EDIT: Only checks first line and prints rest in a new file if the header exists. If not, the original is unchanged.

Answer 5

sed '/id name job_id/d' fileName