putenv(3) [osf1 man page]
putenv(3) Library Functions Manual putenv(3) NAME
putenv - Sets an environment variable LIBRARY
Standard C Library (libc.so, libc.a) SYNOPSIS
#include <stdlib.h> int putenv( const char *string); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: putenv(): XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Points to a name=value string. DESCRIPTION
The putenv() function sets the value of an environment variable by altering an existing variable or by creating a new one. The new envi- ronment variable remains in effect even after the program setting it is exited. The string parameter points to a string of the form "name=value", where name is the environment variable and value is the new value for it. NOTES
The putenv() function manipulates the environ external variable, and it can be used in conjunction with the getenv() function. However, the third parameter to the main function (the environment pointer) is not changed. The putenv() function uses the malloc() function to enlarge the environment. A potential error is to call putenv() with an automatic variable as the argument and then exit the calling function while string is still part of the environment. RETURN VALUES
Upon successful completion, a value of 0 (zero) is returned. If the malloc() function is unable to obtain sufficient space to expand the environment, the putenv() function returns a nonzero value. RELATED INFORMATION
Functions: clearenv(3), exec(2), getenv(3), malloc(3) Standards: standards(5) delim off putenv(3)
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putenv(3C) Standard C Library Functions putenv(3C) NAME
putenv - change or add value to environment SYNOPSIS
#include <stdlib.h> int putenv(char *string); DESCRIPTION
The putenv() function makes the value of the environment variable name equal to value by altering an existing variable or creating a new one. In either case, the string pointed to by string becomes part of the environment, so altering the string will change the environment. The string argument points to a string of the form name=value. The space used by string is no longer used once a new string-defining name is passed to putenv(). The putenv() function uses malloc(3C) to enlarge the environment. After putenv() is called, environment variables are not in alphabetical order. RETURN VALUES
Upon successful completion, putenv() returns 0. Otherwise, it returns a non-zero value and sets errno to indicate the error. ERRORS
The putenv() function may fail if: ENOMEM Insufficient memory was available. USAGE
The putenv() function can be safely called from multithreaded programs. Caution must be exercised when using this function and getenv(3C) in multithreaded programs. These functions examine and modify the environment list, which is shared by all threads in a program. The sys- tem prevents the list from being accessed simultaneously by two different threads. It does not, however, prevent two threads from succes- sively accessing the environment list using putenv() or getenv(). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Safe | +-----------------------------+-----------------------------+ SEE ALSO
exec(2), getenv(3C), malloc(3C), attributes(5), environ(5), standards(5) WARNINGS
The string argument should not be an automatic variable. It should be declared static if it is declared within a function because it can- not be automatically declared. A potential error is to call putenv() with a pointer to an automatic variable as the argument and to then exit the calling function while string is still part of the environment. SunOS 5.11 7 Aug 2004 putenv(3C)