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# C Language Functions

Many standard C Runtime functions can be used in Vuser scripts that are in the C language. Expand the categories to locate the desired function.

String Manipulation Functions

Buffer Manipulation Functions

Process Control Functions

Memory Allocation Functions

Mathematics Functions

Input-Output Functions

File Manipulation Functions

Date and Time Functions

Data Type Conversion Functions

Character Classification and Conversion Functions

Alphabetical Listing of C Functions

Keywords

## Limitations

- If you try to create a buffer that is too large or if the total size of the local variables is to large, the C interpreter throws an error "Too many local variables" instead of indicating that the buffer is too large. For example, this is an error`: char buffer[4096*8];`.

  To allocate large buffers, use malloc instead of declaring the buffer as a local variable.

- In Vugen scripts, you need to explicitly declare C functions that do not return integers. For example, put the following near the beginning of a script that uses the C function strtok:
  `extern char* strtok(char *`token`, const char *`delimiter`);`
- In Linux C scripting, `wchar_t` and functions returning a `struct` or `union` are not supported for functions from external libraries. For example, div_t div(int a, int b) is not supported.

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