Torsten Bögershausen <tbo...@web.de> writes: > Thanks for an interesting reading, > please allow a side question: > Could it be, that "-1 == unlimited" is Linux specific? > And therefore not 100% portable ? > > And doesn't "unlimited" number of files call for trouble, > having the risk to starve the machine ? > > BTW: cygwin returns 256.
If you look at the caller, you will see that we do cap the value returned from this helper function down to a more reasonable and not so selfish maximum, exactly for the purpose of avoiding the risk of starving other processes. > > ------------ > http://pubs.opengroup.org/onlinepubs/007908799/xsh/sysconf.html > RETURN VALUE > > If name is an invalid value, sysconf() returns -1 and sets errno to > indicate the error. If the variable corresponding to name is associated with > functionality that is not supported by the system, sysconf() returns -1 > without changing the value of errno. That is a rather dated document. POSIX.1-2013 (look for the URL to the corresponding page in an earlier message from me) has a bit tighter wording than that to clarify the "there is no limit" case. In addition, the final version Peff and I worked out does not even look at the value of errno, in order not to rely on possibly ambiguous interpretations of negative return values. So I think we are good. Thanks. > ---------- Mac OS, based on BSD (?): ---------- > RETURN VALUES > If the call to sysconf() is not successful, -1 is returned and errno is > set appropriately. Otherwise, if the variable is associated with func- > tionality that is not supported, -1 is returned and errno is not modi- > fied. Otherwise, the current variable value is returned. > > ERRORS > The sysconf() function may fail and set errno for any of the errors spec- > ified for the library function sysctl(3). In addition, the following > error may be reported: > > [EINVAL] The value of the name argument is invalid. > [snip] > The sysconf() function first appeared in 4.4BSD. > > ----------- > Linux, Debian: > OPEN_MAX - _SC_OPEN_MAX > The maximum number of files that a process can have open at any > time. Must not be less than _POSIX_OPEN_MAX (20). > [snip] > RETURN VALUE > If name is invalid, -1 is returned, and errno is set to EINVAL. Other‐ > wise, the value returned is the value of the system resource and errno > is not changed. In the case of options, a positive value is returned > if a queried option is available, and -1 if it is not. In the case of > limits, -1 means that there is no definite limit. -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html