string sed 替换第一行中的字符串
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sed replace string in a first line
提问by irek
How can I replace a string but only in the first line of the file using the program "sed"?
如何使用程序“sed”替换文件的第一行中的字符串？
The commands s/test/blah/1and 1s/test/blah/don't seem to work. Is there another way?
命令s/test/blah/1和1s/test/blah/似乎不起作用。还有其他方法吗？
回答by potong
This might work for you (GNU sed):
这可能对你有用（GNU sed）：
sed -i '1!b;s/test/blah/' file
will only substitute the first testfor blahon the first line only.
只会替换第一个test用于blah仅在第一线。
Or if you just want to changethe first line:
或者，如果您只想更改第一行：
sed -i '1c\replacement' file
回答by Chris Seymour
This will do it:
这将做到：
sed -i '1s/^.*$/Newline/' textfile.txt
Failing that just make sure the match is unique to line one only:
如果失败，请确保匹配仅对第一行是唯一的：
sed -i 's/this is line one and its unique/Changed line one to this string/' filename.txt
The -ioption writes the change to the file instead of just displaying the output to stdout.
该-i选项将更改写入文件，而不仅仅是将输出显示到标准输出。
EDIT:
编辑：
To replace the whole line by matching the common string would be:
通过匹配公共字符串来替换整行将是：
sed -i 's/^.*COMMONSTRING$/Newline/'
Where ^matches the start of the line, $matches the end of the line and .*matches everything upto COMMONSTRING
Where^匹配行的开头，$匹配行的结尾并.*匹配所有内容COMMONSTRING
回答by Hymantrade
this replaces all matches, not just the first match, only in the first line of course:
这将替换所有匹配项，而不仅仅是第一个匹配项，当然仅在第一行中：
sed -i '1s/test/blah/g' file
the /g did the trickto replace more than one matches, if any exists.
/g可以替换多个匹配项（如果存在）。
