C getenv() function C getenv() function - Get value of an environment variable Syntax getenv() function char *getenv(const char *varname) The getenv() function is used to search the list of environment variables
return 0; } 编译运行如下: root@leo:demo# gcc getenv.c -o getenv && .../getenv getenv.c: In function ‘main’: getenv.c:4:12: warning: initialization makes pointer from integer...于是先man一下这个函数,解释如下: GETENV(3) Linux Programmer's Manual...GETENV(3) NAME getenv, secure...
The getenv() function in C++ returns a pointer to a C string containing the value of the environment variable passed as argument.
IfvarnameisNULL, this function invokes an invalid parameter handler, as described inParameter validation. If execution is allowed to continue, this function setserrnotoEINVALand returnsNULL. _wgetenvis a wide-character version ofgetenv; the argument and return value of_wgetenvare wide-character str...
On POSIX systems, theenvironment variablesare also accessible through the global variableenviron, declared asexternchar**environ;in<unistd.h>, and through the optional third argument,envp, ofthe main function. The call togetenv_swith a null pointer forvalueand zero forvalueszis used to determine ...
On POSIX systems, the environment variables are also accessible through the global variable environ, declared as extern char** environ; in <unistd.h>, and through the optional third argument, envp, of the main function. Example Run this code #include <cstdlib> #include <iostream> int main(...
If varname is NULL, this function invokes an invalid parameter handler, as described in Parameter validation. If execution is allowed to continue, this function sets errno to EINVAL and returns NULL._wgetenv is a wide-character version of getenv; the argument and return value of _wgetenv are...
On POSIX systems, theenvironment variablesare also accessible through the global variableenviron, declared asexternchar**environ;in<unistd.h>, and through the optional third argument,envp, ofthe main function. The call togetenv_swith a null pointer forvalueand zero forvalueszis used to determine ...
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expand all in page Description Rule Definition The pointer returned by the C++ Standard Library functions asctime, ctime, gmtime, localtime, localeconv, getenv, setlocale or strerror must not be used following a subsequent call to the same function. 1 Rationale The C Standard allows nonreentrant...