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bash中的冒号是内建命令

“:” is a builtin shell command, and is equivalent to to the “true” command, it is used mostly as a placeholder in scripts.

永远返回真, 相当于一个站位符号.

可以用来注释,跨行注释

: ‘this is
comment
!!’

如下是一个有冒号的,看似是一个命令. 会不断fork线程,导致机器崩溃.
但实际上, 这个和冒号命令无关.

:(){ :|:& };:

: 这里代表是定义了一个函数名字而已. 和下面的一段bash代码意义相同.

funcname() {
# Run 2 instances of the very same function
# in the background. Each of these new
# processes will do the same: each starts 2 new
# processes doing the same,... and again, and again..
funcname | funcname &
}

STUB: dont run this! It will probably halt your computer.

# Now just call the function to start forking
# bash processes indefinately.

funcname

# We will never get here.

如何让机器死机?

Perl exmaple:
perl -e "fork while fork" &
Python example:
import os
while(1):
os.fork()
Windows XP / Vista bat file example:
:bomb
start %0
goto bomb
UNIX style for Windows:
%0|%0

C program example:

#include
int main() { while(1) fork(); }
Plz note that the fork bomb is a form of denial of service, so don’t run on production or unauthorized system.