使用sed或awk在两个匹配模式之间插入行

Question

I have lines in text.txt as follows

start:xfedfgrrg
vfefvrgvr
efefrg
end: abc
end : xyz

start:ewef
feefvef
frrfer
end:ccbf


start:e3frrf
f2erv
frf
end: ece
end: d32d2d
end: fff

I want to add few lines (let's say hello world) everytime patten "end:" matches. But ignore following occurrence of pattern "end:" untill a "start:" pattern matches again.

Required Output

start:xfedfgrrg
vfefvrgvr
efefrg
hello world
end: abc
end : xyz

start:ewef
feefvef
frrfer
hello world
end:ccbf


start:e3frrf
f2erv
frf
hello world
end: ece
end: d32d2d
end: fff

Answer 1

Awk oneliner:

awk '/start:/{on=1} on&&/end:/{print "hello world"; on=0} {print}' file

which uses a variable "on" to mark when we're between the start/end blocks.

Answer 2

$ sed '/start/{x;s/.*/./;x};/end/{x;/^.$/{x;s/^/hello world\n/;x};s/^/./;x}' filename
start:xfedfgrrg
vfefvrgvr
efefrg
hello world
end: abc
end : xyz

start:ewef
feefvef
frrfer
hello world
end:ccbf


start:e3frrf
f2erv
frf
hello world
end: ece
end: d32d2d
end: fff

Explanations :

like this

if (/start/)
    HoldSpace = "."

if (/end/)
    if (HoldSpace == ".")  # just one /end/
        add "hello world\n" to first

    HoldSpace = HoldSpace + "."  # if two /end/; HoldSpace is ".."