从特定行开始在文件中插入行

Question

我想从特定行开始在bash中插入行.

每一行都是一个字符串,它是一个数组的元素

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

而具体的行是'字段'

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

Answer 1

这可以用sed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

使用-i保存在原地,而不是印刷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test.txt文件中添加一个新行：

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

绝对是在这种情况下，您想使用类似sed（或awk或perl）的东西，而不是一次在Shell循环中读取一行。这不是外壳能很好或有效地完成的事情。

您可能会发现编写可重用的函数很方便。这是一个简单的示例，尽管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：

$ 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.
$