Determine string-valued system configuration options.
Syntax |
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#include <unistd.h>
size_t confstr(int name, char *buf, size_t len);
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Parameters |
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- name
Specifies the system configuration option, the string
value of which you want to obtain. The value of name
may be any one of a set of symbols defined in
<unistd.h>; each of these symbols corresponds to a
system configuration option. Possible symbols are:
- _CS_PATH
This name is used to return a value for the PATH
environment variable that can find all the POSIX.2
standard utilities.
- _CS_SHELL
This name is used to find the path name to the
standard shell command line interpreter.
- buf
Points to the region of memory where confstr() stores
the string value of the variable indicated by name.
- len
Is the maximum number of characters that can be placed
in buf. If this is not enough to hold the complete
string value of name, confstr() truncates the string
value to len-1 characters and appends a null terminator
(the \0 character).
Return Values |
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The confstr() function returns configuration-defined
string values.
If name is not a configuration defined value, then confstr() returns 0 and sets errno.
Description |
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confstr() is for options that have a string value; for options with a numeric value, use sysconf(). Unless there is an error, confstr() returns the length of the configuration defined string, including the null
termination character. This may be greater than len if
len wasn't big enough to hold the entire string value.
If len is zero and buf is a NULL pointer, confstr() does not attempt to return a string but does return the appropriate length. In this way, you can use the value to allocate sufficient memory to hold the string.
Errors |
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If an error occurs, errno is set to one of the following values:
| EINVAL | CAUSE | The value specified for the name argument was invalid. |
| | ACTION | Specify a valid name. |
If name has a configuration defined value, confstr() returns the size of the buffer required to hold that value. If this return value is greater than len, confstr() truncates the string returned in buf.
See Also |
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sysconf(), POSIX.2
