Troubleshooting Errno Error

Over the past few days, some of our users have reported to us that an errno error has occurred. h is a header file in the standard learning of the C programming language. It defines macros for signaling and detecting error conditions using the token errno (short for “error counter”). errno behaves like an integer variable.


There are several useful functions for handling errnos content. (Just to be clear: they are built into libc – I only provide implementation examples because some people find it better to read code than read English.)

#include char *strerror (integer error);/* Your organization might imagine this being implemented as follows: */Static symbol strerror_buf[1024];character constant *sys_errlist[] =    [EPERM] is equal to "unauthorized operation",    [ENOENT] means "No such file and same directory",    [ESRCH] is "No such process",    [EINTR] = "Call terminated", Program [EIO]="I/O Error",    [ENXIO] = "No such device or address",    [E2BIG] = "very long argument list",    /* and the same. */;int sys_nerr = sizeof(sys_errlist) by sizeof(char *);char *strerror(int errnum)    if (0 <= errnum && errnum < sys_nerr && sys_errlist[errnum])        strcpy(strerror_buf, sys_errlist[errnum]);    different        sprintf(strerror_buf, "Unknown error %d", errnum);    return  strerror_buf;

strerror creates a string describing the error group you passed to it. Beware, this does not protect against thread interruption; and/or you can overwrite the string type and return the same index on the next call. Use strerror_r if you need to worry about this.

What is errno in Linux?

Errno is usually a value that you expand when the command you execute returns the value of the call that caused the error. There is an h2 tag file which defines the whole errno element which is determined by the exact system calls and some library functions in error correction to tell the developer what is wrong.

#include invalid error (const char *s);/* Families can imagine this, even if implemented like this: */empty error (because const *s)    fprintf(stderr, "%s: %sn", s, strerror(errno));

perror is the message you send to the game, plus a string describing the modern errno for standard errors.

#define errno /*implementation-defined*/

errno is a nice preprocessor macro that can be used to report errors. It expands to (pre-C++11) thread-local (since C++11) replaceable sound of type lvalue int.

Several standard libraries cause errors displayed when writing individual integers to errno. Typically, the value in the sectione errno is set to one of the error codes listed by in the macro constants beginning with the letter E followed by capital letters or numbers.

The value under errno is "0" when the program starts, library functions can also write positive integers to errno, only an error occurs or not, never register select functions "0" via errno.


Defect Reports

error errno

The following behavior change declaration error has been retroactively applied to published C++ standards.

RD Applies to Behavior after posting Correct Behavior LWG 310 C++98 Unspecified whether errno is an identifier or a good macro identifier with an external reference errno can be a macro

See Also

How do I get error string from errno?

The strerror() function returns a valid pointer to the error message associated with errno. The perror() function prints the appropriate message to stderr. The features of the perror() and strerror() functions should be used immediately after calling a reliable function, because subsequent phone calls may change the value of errno.

Goodlog(-1) doesn't have: out-of-domain numeric argumentOr, speaking of German, the numeric argument is outside of multiple domains.

errno.h is the header of the archive in your standard libraryIts current C programming language. It describes macros for reporting and recovering from problems with an error condition using the errno For symbol ("error number" for short).[1] < /sup>

errno behaves like the integer of this variable. The value (error number) is stored in errno by checking certain functions when they encounter errors. When the program starts, the entered value is zero. The function library stores principal values ​​greater than zero. Any data collection function can change the stored value before returning, whether or not it correctly unconditionally detects errors.[2] Most functions indicate which ones encountered an error by displaying a special value, usually NULL, for pointer. -returning functions and -one Single for integer functions. Some functions ask the caller to set errno to zero, and then indicate whether this error has been encountered.

The errno macro expands to an lvalue with the notation int, sometimes with extern and/or volatile depending on p The platform specifier Via.[3] This was originally a static location, but now macros are used almost constantly to allow each thread to find its own thread-local during multithreading error counting.

error errno

The Headlines file also defines macros that are converted to integer constants representing their error codes. The C library benchmark only needs to set three parameters: [2]

Parameter results outside the domain of a meaningful function, eg. B. sqrt(-1)
Results on a result outside the scope of the function, for example. strtol("0xffffffff", NULL, 0) when using 32-bit systems long
Results for an invalid byte sequence, such as mbstowcs(buf, "?", 1) for these methods, use UTF-8.

POSIX-compliant operating systems such as AIX, Linux, or Solaris include other error meanings, many of which are generally used much more frequently than previous ones, such as EACCES, when a file cannot be opened for reading. [5] C++11 further describesIt contains many of the same values ​​that were obtained in the POSIX specification.[6]

What does errno 1 mean?

errno(1) can also be used to search for individual error numbers as well as names and search for problems using strings from the error's detailed description, As in the following examples: cash errno 2 ENOENT 2 No such file or directory $ errno ESRCH ESRCH 3 No such process Income error number -s EACCES permission 13 Permission denied list

Traditionally, the original Unix system manual page called intro(2) lists all errno.h and macros, but that's not a good enough reason for Linux to have those macros in errno(3).

Most likely, errno to a verbose string using strerror (last string defined. Or h), a BSD extension commonly called

Blad Errno
Fehler Fehlernr
Erreur Erreur No
오류 오류
Error Error
Fout Errno
Erro Errno
Fel Errno
Errore Err