bash - 从特定行开始在文件中插入行

Question

我想从特定行开始在 bash 中的文件中插入行。

每行都是一个字符串，它是数组的一个元素

line[0]="foo"
line[1]="bar"
...

并且具体的行是'fields'

file="$(cat $myfile)"
for p in $file; do
    if [ "$p" = 'fields' ]
        then insertlines()     #<- here
    fi
done

Answer 1

这可以通过 sed 来完成：sed 's/fields/fields\nNew Inserted Line/'

$ cat file.txt 
line 1
line 2 
fields
line 3
another line 
fields
dkhs

$ sed 's/fields/fields\nNew Inserted Line/' file.txt 
line 1
line 2 
fields
New Inserted Line
line 3
another line 
fields
New Inserted Line
dkhs

用于-i就地保存而不是打印到stdout

sed -i 's/fields/fields\nNew Inserted Line/'

作为 bash 脚本：

#!/bin/bash

match='fields'
insert='New Inserted Line'
file='file.txt'

sed -i "s/$match/$match\n$insert/" $file

Answer 2

或者另一个例子sed：

准备一个test.txt文件：

echo -e "line 1\nline 2\nline 3\nline 4" > /tmp/test.txt

cat /tmp/test.txt
line 1
line 2
line 3
line 4

在文件中添加新行test.txt：

sed -i '2 a line 2.5' /tmp/test.txt
# sed for in-place editing (-i) of the file: 'LINE_NUMBER a-ppend TEXT_TO_ADD'

cat /tmp/test.txt
line 1
line 2
line 2.5
line 3
line 4

Answer 3

这绝对是您想要使用sed（或awk或perl）之类的东西而不是在shell循环中一次读取一行的情况。这不是 shell 做得好的或有效的事情。

您可能会发现编写可重用函数很方便。这是一个简单的，虽然它不适用于完全任意的文本（斜杠或正则表达式元字符会混淆事物）：

function insertAfter # file line newText
{
   local file="$1" line="$2" newText="$3"
   sed -i -e "/^$line$/a"$'\\\n'"$newText"$'\n' "$file"
}

例子：

$ cat foo.txt
Now is the time for all good men to come to the aid of their party.
The quick brown fox jumps over a lazy dog.
$ insertAfter foo.txt \
   "Now is the time for all good men to come to the aid of their party." \
   "The previous line is missing 'bjkquvxz.'"
$ cat foo.txt
Now is the time for all good men to come to the aid of their party.
The previous line is missing 'bjkquvxz.'
The quick brown fox jumps over a lazy dog.
$ 

Answer 4

sed 是你的朋友：

:~$ cat text.txt 
foo
bar
baz
~$ 

~$ sed '/^bar/\na this is the new line/' text.txt > new_text.txt
~$ cat new_text.txt 
foo
bar
this is the new line
baz
~$