What is Getenv in C?

What is Getenv in C?

The getenv() function shall search the environment of the calling process (see the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 8, Environment Variables) for the environment variable name if it exists and return a pointer to the value of the environment variable.

What does the Getenv () function do?

The getenv() function returns a pointer to the string containing the value for the specified varname in the current environment. If getenv() cannot find the environment string, NULL is returned, and errno is set to indicate the error.

What does Getenv mean?

The getenv() function searches the environment list to find the environment variable name, and returns a pointer to the corresponding value string. The GNU-specific secure_getenv() function is just like getenv() except that it returns NULL in cases where “secure execution” is required.

Do I have to free Getenv?

You should not free it. This is a snippet from the man page: As typically implemented, getenv() returns a pointer to a string within the environment list. The caller must take care not to modify this string, since that would change the environment of the process.

Is Getenv null terminated?

This function returns a null-terminated string with the value of the requested environment variable, or NULL if that environment variable does not exist.

Is Getenv a Syscall?

If your getenv function call is invisible to it, it is not a system call.

Is Getenv portable?

The string pointed by the pointer returned by this function shall not be modified by the program. Some systems and library implementations may allow to change environmental variables with specific functions ( putenv , setenv…), but such functionality is non-portable.

Is Getenv thread safe?

This function is thread-safe (calling it from multiple threads does not introduce a data race) as long as no other function modifies the host environment. In particular, the POSIX functions setenv(), unsetenv(), and putenv() would introduce a data race if called without synchronization.

Does Getenv return strings?

RETURN VALUE Upon successful completion, getenv() returns a pointer to a string containing the value for the specified name.

Is Putenv thread safe?

Although putenv() is threadsafe, if a thread calls an environment variable function while another thread is accessing an environment variable from the environ array the thread may see undefined results.

How to use getenv () function in C?

The C library function char *getenv (const char *name) searches for the environment string pointed to by name and returns the associated value to the string. Following is the declaration for getenv () function.

What happens to the Pointer returned by getenv?

The pointer returned points to an internal memory block, whose content or validity may be altered by further calls to getenv (but not by other library functions). The string pointed by the pointer returned by this function shall not be modified by the program.

How to retrieve the value of an environment variable in C?

The function will retrieve a C string that is containing a value of the environment variable, which is specified with the name argument. The name of the variable that you want to get. If the requested variable is not part of the environment list, the function returns a NULL pointer. This entry was posted in C Reference stdlib.h Functions .

What happens if getenv () returns null?

successful. here PATH is not found for getenv (). SO it will return NULL. @sivaraman – That is not correct, if null is returned then no environment path is found. If it is not null then an environment path is found. If I compile the sample then the output on a Windows 7 system is: