Posix File System Error Codes
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DESCRIPTION top The
Posix Error Codes
error to indicate what went wrong. Its value is significant only when the return value of the call indicated
Errno.h In C
an error (i.e., -1 from most system calls; -1 or NULL from most library functions); a function that succeeds is allowed to change errno. Valid error numbers are all nonzero; errno
Errno.h Linux Kernel
is never set to zero by any system call or library function. For some system calls and library functions (e.g., getpriority(2)), -1 is a valid return on success. In such cases, a successful return can be distinguished from an error return by setting errno to zero before the call, and then, if the call returns a status that indicates that an error linux errno to string may have occurred, checking to see if errno has a nonzero value. errno is defined by the ISO C standard to be a modifiable lvalue of type int, and must not be explicitly declared; errno may be a macro. errno is thread-local; setting it in one thread does not affect its value in any other thread. All the error names specified by POSIX.1 must have distinct values, with the exception of EAGAIN and EWOULDBLOCK, which may be the same. Below is a list of the symbolic error names that are defined on Linux. Some of these are marked POSIX.1, indicating that the name is defined by POSIX.1-2001, or C99, indicating that the name is defined by C99. E2BIG Argument list too long (POSIX.1) EACCES Permission denied (POSIX.1) EADDRINUSE Address already in use (POSIX.1) EADDRNOTAVAIL Address not available (POSIX.1) EAFNOSUPPORT Address family not supported (POSIX.1) EAGAIN Resource temporarily unavailable (may be the same value as EWOULDBLOCK) (POSIX.1) EALREADY Connection already in progress (POSIX.1) EBADE Invalid exchange EBADF Bad file descriptor (POSIX.1) EBADFD File descriptor in bad state EBADMSG Bad message (POSIX.1) EBADR Invalid request descript
In C programming language, there is no direct support for error handling. You have to detect the failure and handle the error. In C programming language, return values represents success or failure. errno 0 Inside a C program, when a function fails, you should handle the errors accordingly, ebadf or at least record the errors in a log file. When you are running some program on Linux environment, you might efault notice that it gives some error number. For example, "Error no is : 17", which doesn't really say much. You really need to know what error number 17 means. This article shows all available error http://man7.org/linux/man-pages/man3/errno.3.html numbers along with it descriptions. This article might be a handy reference for you, when you encounter an error number and you would like to know what it means. In C programming language, there is an external variable called "errno". From this errno variable you can use some error handling functions to find out the error description and handle it appropriately. You have to include errno.h header file to use external http://www.thegeekstuff.com/2010/10/linux-error-codes variable errno. perror function prints error description in standard error. The strerror function returns a string describing the error code passed in the argument errnum. The following C code snippet tries to open a file through open system call. There are two flags in the open call. O_CREAT flag is to create a file, if the file does not exist. O_EXCL flag is used with O_CREAT, if the file is already exist open call will fail with the proper error number. $ cat fileopen.c #include
Signals Alternative tokens Miscellaneous headers