Function Write Error Codes
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codes can’t occur on GNU systems, but they can occur using the GNU C Library on other systems. Macro: int EPERM Operation not permitted; linux kernel error codes only the owner of the file (or other resource) or processes with c programming error codes special privileges can perform the operation. Macro: int ENOENT No such file or directory. This is a “file doesn’t c error function exist” error for ordinary files that are referenced in contexts where they are expected to already exist. Macro: int ESRCH No process matches the specified process ID. Macro: int EINTR eintr errno Interrupted function call; an asynchronous signal occurred and prevented completion of the call. When this happens, you should try the call again. You can choose to have functions resume after a signal that is handled, rather than failing with EINTR; see Interrupted Primitives. Macro: int EIO Input/output error; usually used for physical read or write errors. Macro: int ENXIO No such
Enosys Error
device or address. The system tried to use the device represented by a file you specified, and it couldn’t find the device. This can mean that the device file was installed incorrectly, or that the physical device is missing or not correctly attached to the computer. Macro: int E2BIG Argument list too long; used when the arguments passed to a new program being executed with one of the exec functions (see Executing a File) occupy too much memory space. This condition never arises on GNU/Hurd systems. Macro: int ENOEXEC Invalid executable file format. This condition is detected by the exec functions; see Executing a File. Macro: int EBADF Bad file descriptor; for example, I/O on a descriptor that has been closed or reading from a descriptor open only for writing (or vice versa). Macro: int ECHILD There are no child processes. This error happens on operations that are supposed to manipulate child processes, when there aren’t any processes to manipulate. Macro: int EDEADLK Deadlock avoided; allocating a system resource would have resulted in a deadlock situation. The system does not guarantee th
and Signals and Traps (Oh My!) - Part 1 by William Shotts, Jr. In this lesson, we're going to look at handling errors during the execution of your scripts. The difference between a good program and a poor one is often measured in terms of the
Eintr Signal
program's robustness. That is, the program's ability to handle situations in which something goes wrong. eio error in c Exit status As you recall from previous lessons, every well-written program returns an exit status when it finishes. If a program finishes successfully, posix error codes the exit status will be zero. If the exit status is anything other than zero, then the program failed in some way. It is very important to check the exit status of programs you call in your scripts. It http://www.gnu.org/s/libc/manual/html_node/Error-Codes.html is also important that your scripts return a meaningful exit status when they finish. I once had a Unix system administrator who wrote a script for a production system containing the following 2 lines of code: # Example of a really bad idea cd $some_directory rm * Why is this such a bad way of doing it? It's not, if nothing goes wrong. The two lines change the working directory to the name contained in $some_directory and delete http://linuxcommand.org/wss0150.php the files in that directory. That's the intended behavior. But what happens if the directory named in $some_directory doesn't exist? In that case, the cd command will fail and the script executes the rm command on the current working directory. Not the intended behavior! By the way, my hapless system administrator's script suffered this very failure and it destroyed a large portion of an important production system. Don't let this happen to you! The problem with the script was that it did not check the exit status of the cd command before proceeding with the rm command. Checking the exit status There are several ways you can get and respond to the exit status of a program. First, you can examine the contents of the $? environment variable. $? will contain the exit status of the last command executed. You can see this work with the following: [me] $ true; echo $? 0 [me] $ false; echo $? 1 The true and false commands are programs that do nothing except return an exit status of zero and one, respectively. Using them, we can see how the $? environment variable contains the exit status of the previous program. So to check the exit status, we could write the script this way: # Check the exit status cd $some_directory if [ "$?" = "0" ]; then rm * else echo "Cannot change
not all, available error codes in libcurl. Why they occur and possibly what you can do to fix the problem are also included. CURLcode Almost all "easy" interface functions return a CURLcode https://curl.haxx.se/libcurl/c/libcurl-errors.html error code. No matter what, using the curl_easy_setopt option CURLOPT_ERRORBUFFER is a good idea https://en.wikipedia.org/wiki/Write_(system_call) as it will give you a human readable error string that may offer more details about the cause of the error than just the error code. curl_easy_strerror can be called to get an error string from a given CURLcode number. CURLcode is one of the following: CURLE_OK (0) All fine. Proceed as usual. CURLE_UNSUPPORTED_PROTOCOL (1) error codes The URL you passed to libcurl used a protocol that this libcurl does not support. The support might be a compile-time option that you didn't use, it can be a misspelled protocol string or just a protocol libcurl has no code for. CURLE_FAILED_INIT (2) Very early initialization code failed. This is likely to be an internal error or problem, or a resource problem where something fundamental couldn't get function write error done at init time. CURLE_URL_MALFORMAT (3) The URL was not properly formatted. CURLE_NOT_BUILT_IN (4) A requested feature, protocol or option was not found built-in in this libcurl due to a build-time decision. This means that a feature or option was not enabled or explicitly disabled when libcurl was built and in order to get it to function you have to get a rebuilt libcurl. CURLE_COULDNT_RESOLVE_PROXY (5) Couldn't resolve proxy. The given proxy host could not be resolved. CURLE_COULDNT_RESOLVE_HOST (6) Couldn't resolve host. The given remote host was not resolved. CURLE_COULDNT_CONNECT (7) Failed to connect() to host or proxy. CURLE_FTP_WEIRD_SERVER_REPLY (8) The server sent data libcurl couldn't parse. This error code is used for more than just FTP and is aliased as CURLE_WEIRD_SERVER_REPLY since 7.51.0. CURLE_REMOTE_ACCESS_DENIED (9) We were denied access to the resource given in the URL. For FTP, this occurs while trying to change to the remote directory. CURLE_FTP_ACCEPT_FAILED (10) While waiting for the server to connect back when an active FTP session is used, an error code was sent over the control connection or similar. CURLE_FTP_WEIRD_PASS_REPLY (11) After having sent the FTP password to the server, libcurl expects a proper reply. This error code indicates that an unexpected code was returned. CURLE_FTP
a file. This is primary way to output data from a program by directly using a system call. The destination is identified by a numeric code. The data to be written, for instance a piece of text, is defined by a pointer and a size, given in number of bytes. write thus takes three arguments: The file code (file descriptor or fd). The pointer to a buffer where the data is stored (buf). The number of bytes to write from the buffer (nbytes). Contents 1 POSIX usage 2 Usage Example 3 Errors encountered during operation 4 Higher level I/O functions calling write 5 See also 6 References 7 External links POSIX usage[edit] The write system call interface[1][2][3] is standardized by the POSIX specification. Data is written to a file by calling the write function. The function prototype is: ssize_t write(int fd, const void *buf, size_t nbytes); Argument Description fd It is the file descriptor which has been obtained from the call to open. It is an integer value. The values 0, 1, 2 can also be given, for standard input, standard output & standard error, respectively . buf It points to a character array, which can be used to store content obtained from the file pointed to by fd. nbytes It specifies the number of bytes to be written from the character array into the file pointed to by fd. In above syntax, ssize_t is a typedef. It is a signed data type defined in stddef.h. Note that write() does not return an unsigned value; it returns -1 if an error occurs so it must return a signed value. The write function returns the number of bytes successfully written into the array, which may at times be less than the specified nbytes. It returns -1 if an exceptional condition is encountered, see section on errors below. Usage Example[edit] #include