| Wiki Markup |
|---|
C99 defines {{getenv()}} to have the following behavior: \[[ISO/IEC 9899:1999|AA. References#ISOBibliography#ISO/IEC 9899-1999]\] |
The getenv function returns a pointer to a string associated with the matched list member. The string pointed to shall not be modified by the program but may be overwritten by a subsequent call to the getenv function.
...
| Wiki Markup |
|---|
Windows provides the [{{getenv_s()}} and {{\_wgetenv_s()}}|http://msdn.microsoft.com/en-us/library/tb2sfw2z(VS.80).aspx] functions for getting a value from the current environment \[[MSDN|AA. References#MSDNBibliography#MSDN]\]. |
| Code Block | ||
|---|---|---|
| ||
char *tmpvar;
char *tempvar;
size_t requiredSize;
getenv_s(&requiredSize, NULL, 0, "TMP");
tmpvar = (char *)malloc(requiredSize * sizeof(char));
if (!tmpvar) {
/* Handle error */
}
getenv_s(&requiredSize, tmpvar, requiredSize, "TMP" );
getenv_s(&requiredSize, NULL, 0, "TEMP");
tempvar = (char *)malloc(requiredSize * sizeof(char));
if (!tempvar) {
free(tmpvar);
tmpvar = NULL;
/* Handle error */
}
getenv_s(&requiredSize, tempvar, requiredSize, "TEMP" );
if (strcmp(tmpvar, tempvar) == 0) {
if (puts("TMP and TEMP are the same.\n") == EOF) {
/* Handle error */
}
}
else {
if (puts("TMP and TEMP are NOT the same.\n") == EOF) {
/* Handle Error */
}
}
free(tmpvar);
tmpvar = NULL;
free(tempvar);
tempvar = NULL;
|
...
| Wiki Markup |
|---|
Windows also provides the [{{\_dupenv_s()}} and {{\_wdupenv_s()}}|http://msdn.microsoft.com/en-us/library/ms175774.aspx] functions for getting a value from the current environment \[[MSDN|AA. References#MSDNBibliography#MSDN]\]. |
The _dupenv_s() function searches the list of environment variables for a specified name. If the name is found, a buffer is allocated, the variable's value is copied into the buffer, and the buffer's address and number of elements are returned. By allocating the buffer itself, _dupenv_s() and _wdupenv_s() provide a more convenient alternative to getenv_s() and _wgetenv_s().
...
| Wiki Markup |
|---|
POSIX provides the [{{strdup()}}|http://www.opengroup.org/onlinepubs/009695399/functions/strdup.html] function, which can make a copy of the environment variable string \[[Open Group 04|AA. References#OpenBibliography#Open Group 04]\]. The {{strdup()}} function is also included in ISO/IEC PDTR 24731-2 \[[ISO/IEC PDTR 24731-2|AA. References#ISOBibliography#ISO/IEC ISO/IEC PDTR 24731-2]\]. |
...
| Wiki Markup |
|---|
\[[ISO/IEC 9899:1999|AA. References#ISOBibliography#ISO/IEC 9899-1999]\] Section 7.20.4, "Communication with the environment" \[[ISO/IEC PDTR 24731-2|AA. References#ISOBibliography#ISO/IEC PDTR 24731-2-2007]\] \[[MSDN|AA. References#MSDNBibliography#MSDN]\] [{{\_dupenv_s()}} and {{\_wdupenv_s()}}|http://msdn.microsoft.com/en-us/library/ms175774.aspx], [{{getenv_s()}}, {{\_wgetenv_s()}}|http://msdn.microsoft.com/en-us/library/tb2sfw2z(VS.80).aspx] \[[Open Group 04|AA. References#OpenBibliography#Open Group 04]\] Chapter 8, and "Environment Variables", [{{strdup}}|http://www.opengroup.org/onlinepubs/009695399/functions/strdup.html] \[[Viega 03|AA. References#ViegaBibliography#Viega 03]\] Section 3.6, "Using Environment Variables Securely" |
...