System Limits and Options

Prev: times-and-dates Next: retrieving-system-and-process-information

Unix implementations must provide limits on system features and resources, like:

• How many files can a process keep open at one time?
• Does the system have realtime signals?
• What is the largest value for a variable?
• How big of an argument list can a program have?
• How long can a pathname be?

Some values should be determined at compile time and some at runtime. For the runtime cases, sysconf, pathconf, and fpathconf can be used to check for implementation limits and options.

#include <unistd.h>
long sysconf(int name); // Returns value of limit specified by name, or –1 if limit is indeterminate or an error occurred

#include <unistd.h>
long pathconf(const char *pathname, int name);
long fpathconf(int fd, int name); // Both return value of limit specified by name, or –1 if limit is indeterminate or an error occurred