C# - What does "\0" equate to?
I am playing with Pex and one of the parameters it passes into my method is "\0"
.
What does that mean? My guess is an empty string (""
) based on the content of my method. However, if it is the same then why not just use ""
i开发者_如何学JAVAnstead of "\0"
?
Anyone know what it is?
'\0' is a "null character". It's used to terminate strings in C and some portions of C++. Pex is doing a test to see how your code handles the null character, likely looking for the Poison Null Byte security exploit.
Most C# code has nothing to fear; if you pass your string to unmanaged code, however, you may have problems.
Edit:
Just to be explicit... Pex is passing a string containing a null character. This is not a null reference.
It's a string with a null character. Older string libraries — like that used in C or older C++ libraries — used the '\0' character to indicate the end of the string.
Newer environments like .Net use a different system, but there is a lot of history around ending a string with '\0', such that it's a common point of error. Testing libraries like Pex will use it to make sure your program handles it correctly.
It's a string containing the character '\0'. C# doesn't treat this in any particularly special way - it's just unicode character U+0000. If you write:
int firstCodePoint = text[0];
then you'll find firstCodePoint
is 0.
Escape Sequence
\0
Character Name
Null
Unicode Encoding
0x0000
See this link.
A string of length 1, containing the character \u0000 (aka NUL). This character is not treated specially.
In C, which uses \0 to terminate string, you also allocate a string of length 1. In this case the standard string functions will report a length of 0, since the string contains \0 as well as being terminated with it. You could safely modify str[0], or strncat a single character into it.
I just found a good example in which \0
is very important and necessary.
Assume we want to remove the last unwanted ,
in the following code.
for (int i = 0; i < 5; i++)
{
foreach (var a in "Money")
Console.Write($"{a},");
}
If we only add Console.Write("\b\n");
as follows,
for (int i = 0; i < 5; i++)
{
foreach (var a in "Money")
Console.Write($"{a},");
Console.Write("\b\n");
}
The output will be still the same.
But if we add \0
as follows,
for (int i = 0; i < 5; i++)
{
foreach (var a in "Money")
Console.Write($"{a},");
Console.Write("\b\0\n");
}
The unwanted trailing ,
vanishes.
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