table of contents
explain_shmctl(3) | Library Functions Manual | explain_shmctl(3) |
NAME¶
explain_shmctl - explain shmctl(2) errorsSYNOPSIS¶
#include <libexplain/shmctl.h>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 decoded.- 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 argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.
if (shmctl(shmid, command, data) < 0)
{
fprintf(stderr, "%s\n", explain_shmctl(shmid, command, data));
exit(EXIT_FAILURE); }
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 better, 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 necessary if you need to call any code between the system call to be explained 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 argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.
if (shmctl(shmid, command, data) < 0)
{ int err = errno;
fprintf(stderr, "%s\n", explain_errno_shmctl(err, shmid, command, data));
exit(EXIT_FAILURE); }
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 better, and indicate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be decoded.- 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.
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); }
explain_message_errno_shmctl¶
void explain_message_errno_shmctl(char *message, int message_size, int errnum, 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 necessary if you need to call any code between the system call to be explained 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.
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); }
SEE ALSO¶
- shmctl(2)
- shared memory control
- explain_shmctl_or_die(3)
- shared memory control and report errors