如何使用sed[closed]仅替换第二个匹配行

跟随 awk 也可以帮你。

awk -v line=2 '$1=="dog" && ++count==line{$1="big_dog"} 1'  Input_file

如果将输出保存到输入文件本身,则追加 > temp_file && mv temp_file Input_file 在上面的代码中。

说明:

awk -v line=2 '             ##Creating an awk variable line whose value is 2 here.
$1=="dog" && ++count==line{ ##Checking condition if $1 is dog and increasing variable count value is equal to value of line(then do following)
  $1="big_dog"}             ##Assigning $1 to big_dog here.
1                           ##awk works on method of condition then action so by mentioning 1 I am making condition TRUE here so by default action print of line will happen.
'  Input_file               ##Mentioning Input_file here.

正如评论中所讨论的,这个替换了第二行的match:

$ sed '2s/dog/big_dog/' your_file
dog cat
big_dog puppy
dog cat

要用sed替换第二个匹配项,请使用:

sed ':a;N;$!ba;s/dog/big_dog/2'   your_file_with_foo_on_first_row_to_demonstrate
foo
dog cat
big_dog puppy
dog cat

sed 替换为第二次出现:

sed "/dog/ {n; :a; /dog/! {N; ba;}; s/dog/big_dog/; :b; n; $! bb}" your_file

说明:

/dog/ {           # find the first occurrence that match the pattern (dog)
  n               # print pattern space and read the next line
  :a              # 'a' label to jump to
  /dog/! {        # if pattern space not contains the searched pattern (second occurrence)
    N             # read next line and add it to pattern space
    ba            # jump back to 'a' label, to repeat this conditional check
  }               # after find the second occurrence...
  s/dog/big_dog/  # do the substitution
  :b              # 'b' label to jump to
  n               # print pattern space and read the next line
  $! bb           # while not the last line of the file, repeat from 'b' label
}

请注意,在找到第二个匹配项后,需要最后3个命令来打印文件的其余部分,否则,搜索模式的每一个偶数匹配项都可能重复替换。

使用下面的命令将单词dog替换为第2行中的big_dog。

# sed -i '2 s/dog/big_dog/g' my_file
# cat my_file
Output:-
dog cat
big_dog puppy
dog cat

如果要从第2个替换为第3个,则可以使用以下命令:

# sed -i '2,3 s/dog/big_dog/g' my_file