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08-20-2001
getenv(3c)
Below is an extract from man page of getenv(3c)
NOTES
1> getenv() can be safely called from a multi-thread program.
2> However, care must still be taken when using getenv() and putenv(3C) in a multi-thread program.
3> These routines examine and modify the environment list.
4> This list is shared by all threads in a program.
5> The system prevents the list from being accessed simultaneously by two different threads.
6> However, it does not prevent two threads from successively accessing the environment list using getenv() or putenv(3C)
1a.) Does Line 5 means that at any one time, the system(OS) allows only one thread to read the ENV list?
1b.) If this is true, in the situation when there are many processes trying getenv() at the same time, will that cause a bottleneck (caused by queuing)?
2.) What does Line 6 means? Does it mean 2 differents thread can access ENV list sqeuentially?
Thnx
NOTES
1> getenv() can be safely called from a multi-thread program.
2> However, care must still be taken when using getenv() and putenv(3C) in a multi-thread program.
3> These routines examine and modify the environment list.
4> This list is shared by all threads in a program.
5> The system prevents the list from being accessed simultaneously by two different threads.
6> However, it does not prevent two threads from successively accessing the environment list using getenv() or putenv(3C)
1a.) Does Line 5 means that at any one time, the system(OS) allows only one thread to read the ENV list?
1b.) If this is true, in the situation when there are many processes trying getenv() at the same time, will that cause a bottleneck (caused by queuing)?
2.) What does Line 6 means? Does it mean 2 differents thread can access ENV list sqeuentially?
Thnx
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LEARN ABOUT SUNOS
getenv
getenv(3C) Standard C Library Functions getenv(3C) NAME
getenv - return value for environment name SYNOPSIS
#include <stdlib.h> char *getenv(const char *name); DESCRIPTION
The getenv() function searches the environment list (see environ(5)) for a string of the form name=value and, if the string is present, returns a pointer to the value in the current environment. RETURN VALUES
If successful, getenv() returns a pointer to the value in the current environment; otherwise, it returns a null pointer. USAGE
The getenv() function can be safely called from a multithreaded application. Care must be exercised when using both getenv() and putenv(3C) in a multithreaded application. These functions examine and modify the environment list, which is shared by all threads in an application. The system prevents the list from being accessed simultaneously by two different threads. It does not, however, prevent two threads from successively accessing the environment list using getenv() or putenv(3C). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Safe | +-----------------------------+-----------------------------+ SEE ALSO
exec(2), putenv(3C), attributes(5), environ(5), standards(5) SunOS 5.10 24 Jul 2002 getenv(3C)