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what is the maximum of number of files c fopen can open at the same time in Linux?
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The default open-file limit is typically 1024. However, in order for FlexNet Code Insight to function properly in a Linux or Unix environment, the open-file limit must be set to handle more than 50K files on each instance hosting the Core Server or a Scan Server.
You can increase the maximum number of open files on the Linux host by setting a new value in the kernel variable file, /proc/sys/fs/file-max. This command forces the limit to 262144 files which is four times the default setting. (The default setting is appropriate for many environments.)
The "Too many open files" message means that the operating system has reached the maximum "open files" limit and will not allow SecureTransport, or any other running applications to open any more files. The open file limit can be viewed with the ulimit command: The ulimit -aS command displays the current limit.
The calls to fopen() and fclose() are blocking and may block for an extended period of time if the file resides on a network drive. While the call is blocked, other threads that are waiting for the lock are also blocked.
The implementation is required to provide FOPEN_MAX in <stdio.h>. This is the minimum number of files the implementation guarantees can be opened simultaneously. You might be able to open more than that, but the only way to know that is to test.
Note that the kernel limit is separate from this -- that tells you how many files you can (potentially) open with open, creat and other OS calls. The standard library of your C implementation can (and often will) impose its own limit (e.g., by statically allocating an array of FILE). In theory, the largest number you can open is the minimum of the limit imposed by the kernel and by the library implementation -- but the kernel's limit is almost always (much) higher.
Generally speaking, if you care about this, you're probably doing something wrong though.
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You can see the maximum allowed open files (kernel limit) by doing:
cat /proc/sys/fs/file-max
Quote from kernel docs:
The value in file-max denotes the maximum number of file- handles that the Linux kernel will allocate. When you get lots of error messages about running out of file handles, you might want to increase this limit.
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