explain_shmctl(3) Library Functions Manual explain_shmctl(3) NAME explain_shmctl - explain shmctl(2) errors SYNOPSIS #include <libexplain/shmctl.h> const char *explain_shmctl(int shmid, int command, struct shmid_ds *data); const char *explain_errno_shmctl(int errnum, int shmid, int command, struct shmid_ds *data); void explain_message_shmctl(char *message, int message_size, int shmid, int command, struct shmid_ds *data); void explain_message_errno_shmctl(char *message, int message_size, int er- rnum, int shmid, int command, struct shmid_ds *data); DESCRIPTION These functions may be used to obtain explanations for errors returned by the shmctl(2) system call. explain_shmctl const char *explain_shmctl(int shmid, int command, struct shmid_ds *data); The explain_shmctl function is used to obtain an explanation of an error returned by the shmctl(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be de- coded. shmid The original shmid, exactly as passed to the shmctl(2) system call. command The original command, exactly as passed to the shmctl(2) system call. data The original data, exactly as passed to the shmctl(2) system call. Returns: The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their ar- gument list. This will be overwritten by the next call to any lib- explain function which shares this buffer, including other threads. Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library. Example: This function is intended to be used in a fashion similar to the following example: if (shmctl(shmid, command, data) < 0) { fprintf(stderr, "%s\n", explain_shmctl(shmid, command, data)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_shm- ctl_or_die(3) function. explain_errno_shmctl const char *explain_errno_shmctl(int errnum, int shmid, int command, struct shmid_ds *data); The explain_errno_shmctl function is used to obtain an explanation of an error returned by the shmctl(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much bet- ter, and indicate the underlying cause in more detail. errnum The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is neces- sary if you need to call any code between the system call to be ex- plained and this function, because many libc functions will alter the value of errno. shmid The original shmid, exactly as passed to the shmctl(2) system call. command The original command, exactly as passed to the shmctl(2) system call. data The original data, exactly as passed to the shmctl(2) system call. Returns: The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their ar- gument list. This will be overwritten by the next call to any lib- explain function which shares this buffer, including other threads. Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library. Example: This function is intended to be used in a fashion similar to the following example: if (shmctl(shmid, command, data) < 0) { int err = errno; fprintf(stderr, "%s\n", explain_errno_shmctl(err, shmid, com- mand, data)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_shm- ctl_or_die(3) function. explain_message_shmctl void explain_message_shmctl(char *message, int message_size, int shmid, int command, struct shmid_ds *data); The explain_message_shmctl function is used to obtain an explanation of an error returned by the shmctl(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much bet- ter, and indicate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be de- coded. message The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe. message_size The size in bytes of the location in which to store the returned message. shmid The original shmid, exactly as passed to the shmctl(2) system call. command The original command, exactly as passed to the shmctl(2) system call. data The original data, exactly as passed to the shmctl(2) system call. Example: This function is intended to be used in a fashion similar to the following example: if (shmctl(shmid, command, data) < 0) { char message[3000]; explain_message_shmctl(message, sizeof(message), shmid, command, data); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_shm- ctl_or_die(3) function. explain_message_errno_shmctl void explain_message_errno_shmctl(char *message, int message_size, int er- rnum, int shmid, int command, struct shmid_ds *data); The explain_message_errno_shmctl function is used to obtain an explanation of an error returned by the shmctl(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail. message The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe. message_size The size in bytes of the location in which to store the returned message. errnum The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is neces- sary if you need to call any code between the system call to be ex- plained and this function, because many libc functions will alter the value of errno. shmid The original shmid, exactly as passed to the shmctl(2) system call. command The original command, exactly as passed to the shmctl(2) system call. data The original data, exactly as passed to the shmctl(2) system call. Example: This function is intended to be used in a fashion similar to the following example: if (shmctl(shmid, command, data) < 0) { int err = errno; char message[3000]; explain_message_errno_shmctl(message, sizeof(message), err, shmid, command, data); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_shm- ctl_or_die(3) function. SEE ALSO shmctl(2) shared memory control explain_shmctl_or_die(3) shared memory control and report errors COPYRIGHT libexplain version 1.3 Copyright (C) 2011 Peter Miller explain_shmctl(3)
NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT
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