std:: getenv
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Defined in header
<cstdlib>
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char
*
getenv
(
const
char
*
env_var
)
;
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Searches the
environment list
provided by the host environment (the OS), for a string that matches the C string pointed to by
env_var
and returns a pointer to the C string that is associated with the matched environment list member.
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This function is not required to be thread-safe. Another call to
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(until C++11) |
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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
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(since C++11) |
Modifying the string returned by
getenv
invokes undefined behavior.
Parameters
| env_var | - | null-terminated character string identifying the name of the environmental variable to look for |
Return value
Character string identifying the value of the environmental variable or null pointer if such variable is not found.
Notes
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
#include <cstdlib> #include <iostream> int main() { if (const char* env_p = std::getenv("PATH")) std::cout << "Your PATH is: " << env_p << '\n'; }
Possible output:
Your PATH is: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
See also
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C documentation
for
getenv
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