How To Get Last Error In Linux
Contents |
DESCRIPTION top The
Linux Errno Example
library functions in the event of an error to indicate what went wrong. how to use errno Its value is significant only when the return value of the call indicated an error (i.e., -1 from most system posix error codes calls; -1 or NULL from most library functions); a function that succeeds is allowed to change errno. Valid error numbers are all nonzero; errno is never set to zero by any system call
Strerror(errno)
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 may have occurred, checking to see if errno has a nonzero value. errno is
Linux Error
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 descriptor EBADRQC Invalid request code EBADSLT Invalid slot EBUSY Device or resource busy (POSIX.1) ECANCELED Operation canceled (POSIX.1) ECHILD No child processes (POSIX.1) ECHRNG Channel number out of range ECOM
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Strerror Example
Overflow the company Business Learn more about hiring developers or posting ads with us Unix & Linux Questions errno.h in c Tags Users Badges Unanswered Ask Question _ Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Join them; http://man7.org/linux/man-pages/man3/errno.3.html it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top How can I get the error code (exit code) of “xdg-mime query filetype” command? up vote 0 down vote favorite I ran xdg-mime query filetype
an error to indicate what went wrong. Its value is significant only when the return value of the call indicated an error (i.e., -1 from most system calls; https://linux.die.net/man/3/errno -1 or NULL from most library functions); a function that succeeds is allowed http://stackoverflow.com/questions/27096985/getting-error-code-when-creating-a-socket-in-linux to change errno. Valid error numbers are all nonzero; errno 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 how to errno to zero before the call, and then, if the call returns a status that indicates that an error 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 how to get 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 descriptor EBADRQC Invalid request code EBADSLT Invalid slot EBUSY Device or resource busy (POSIX.1) ECANCELED Operation canceled (POSIX.1) ECHILD No child processes (POSIX.1) ECHRNG Channel number out of range ECOMM Communication error on send ECONNABORTED Connection aborted (POSIX.1) ECONNREFUSED Connection refused (POSIX.1) ECONNRESET Connection reset (POSIX.1) EDEADLK Resource deadlock avoided (POSIX.1) EDEADLOCK Synonym for EDEADLK EDESTADDRREQ Destination address required (POSIX.1) E
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Getting error code when creating a socket in Linux up vote 0 down vote favorite I'm doing some socket programming in Linux and am wondering how to get the error code when the function socket(...); fails. for example for the "getaddrinfo" function i can do this: //Resolve the server address and port result = (struct addrinfo *) calloc(1, sizeof(struct addrinfo)); iResult = getaddrinfo("google.com", DEFAULT_PORT, &hints, &result); if (iResult != 0){ printf("%d\n", iResult); fprintf(stderr, "getaddrinfo failed: %s\n", gai_strerror(iResult)); getchar(); exit(EXIT_FAILURE); } However I want to do a similar thing using socket(...) function. According to this: http://linux.die.net/man/2/socket the function returns -1 on failure, and sets errno to the appropriate error number. How do i access this "errno" though? This is my code so far: int connectSocket = 0; connectSocket = socket(AF_INET, SOCK_STREAM, 0); printf("%d\n", connectSocket); if (connectSocket == -1){ printf("socket failed with error: %s\n", error_string); //TODO: HELP DECLARING error_string getchar(); exit(EXIT_FAILURE); } Please help. Thanks! yahya c linux sockets share|improve this question asked Nov 24 '14 at 2:23 Yahya Uddin 2,04611440 2 See errno(3) and strerror(3) manual pages. –Nikolai N Fetissov Nov 24 '14 at 2:28 2 DO NOT allocate memory for the addrinfo that you pass in the last parameter of getaddrinfo(). It will allocate the addrinfo for you, which you pass to freeadd