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NAMEexplain_output - output error messagesSYNOPSIS#include <libexplain/output.h>DESCRIPTIONThese functions may be used to write error messages.explain_output_messagevoid explain_output_message(const char *text); The explain_output_message function is used to print text. It is printed via the registered output class, see explain_output_register(3) for how.
explain_output_errorvoid explain_output_error(const char *fmt, ...); The explain_output_error function is used to print a formatted error message. The printing is done via the explain_output_message(3) function.
explain_output_error_and_dievoid explain_output_error_and_die(const char *fmt, ...); The explain_output_error_and_die function is used to print text, and then terminate immediately. The printing is done via the explain_output_message(3) function, process termination is via the explain_output_exit_failure(3) function.
explain_output_warningvoid explain_output_warning(const char *fmt, ...); The explain_output_warning function is used to print a formatted error message, including the word “warning”. The printing is done via the explain_output_message(3) function.
explain_output_exitvoid explain_output_exit(int status); The explain_output_exit function is used to terminate execution. It is executed via the registered output class, explain_output_register(3) for how.
explain_output_exit_failurevoid explain_output_exit_failure(void); The explain_output_exit_failure function is used to terminate execution, with exit status EXIT_FAILURE. It is executed via the registered output class, see explain_output_register(3) for how.explain_option_hanging_indent_setvoid explain_option_hanging_indent_set(int columns); The explain_option_hanging_indent_set function is used to cause the output wrapping to use hanging indents. By default no hanging indent is used, but this can sometimes obfuscate the end of one error message and the beginning of another. A hanging indent results in continuation lines starting with white space, similar to RFC822 headers. This can be set using the “hanging‐indent= n” string in the EXPLAIN_OPTIONS environment variable. See explain(3) for more information. Using this function will override any environment variable setting.
OUTPUT REDIRECTIONIt is possible to change how and where libexplain sends its output, and even how it calls the exit(2) function. This functionality is used by the explain_*_or_die and explain_*_on_error functions. By default, libexplain will wrap and print error messages on stderr, and call the exit(2) system call to terminate execution. Clients of the libexplain library may choose to use some message handling facilities provided by libexplain, or they may choose to implement their own.
To cause all output to be sent to syslog, use
explain_output_register(explain_output_syslog_new());
This is useful for servers and daemons.
The “tee” output class can be used to
duplicate output. To cause all output to be sent to both stderr and syslog,
use
explain_output_register ( explain_output_tee_new ( explain_output_stderr_new(), explain_output_syslog_new() ) );
To cause all output to be sent to both stderr and a
regular file, use
See the <libexplain/output.h> file for extensive documentation.
explain_output_register ( explain_output_tee_new ( explain_output_stderr_new(), explain_output_file_new(filename, 0) ) ); explain_output_newexplain_output_t *explain_output_new(const explain_output_vtable_t *vtable); The explain_output_new function may be used to create a new dynamically allocated instance of explain_output_t.
explain_output_stderr_newexplain_output_t *explain_output_stderr_new(void); The explain_output_stderr_new function may be used to create a new dynamically allocated instance of an explain_output_t class that writes to stderr, and exits via exit(2); This is the default output handler.
explain_output_syslog_newexplain_output_t *explain_output_syslog_new(void); The explain_output_syslog_new function may be used to create a new dynamically allocated instance of an explain_output_t class that writes to syslog, and exits via exit(2); The following values are used:option = 0 facility = LOG_USER level = LOG_ERR
explain_output_syslog_new1explain_output_t *explain_output_syslog_new1(int level); The explain_output_syslog_new1 function may be used to create a new dynamically allocated instance of an explain_output_t class that writes to syslog, and exits via exit(2); The following values are used:option = 0 facility = LOG_USER
explain_output_syslog_new3explain_output_t *explain_output_syslog_new3(int option, int facility, int level); The explain_output_syslog_new3 function may be used to create a new dynamically allocated instance of an explain_output_t class that writes to syslog, and exits via exit(2); If you want different facilities or levels, create multiple instances.
explain_output_file_newexplain_output_t *explain_output_file_new(const char *filename, int append); The explain_output_file_new function may be used to create a new dynamically allocated instance of an explain_output_t class that writes to a file, and exits via exit(2).
explain_output_tee_newexplain_output_t *explain_output_tee_new(explain_output_t *first, explain_output_t *second); The explain_output_tee_new function may be used to create a new dynamically allocated instance of an explain_output_t class that writes to two other output classes.
explain_output_registervoid explain_output_register(explain_output_t *op); The explain_output_register function is used to change libexplain's default output handling facilities with something else. The NULL pointer restores libexplain's default processing. If no output class is registered, the default is to wrap and print to stderr, and to exit via the exit(2) system call.
COPYRIGHTlibexplain version 1.3AUTHORWritten by Peter Miller <pmiller@opensource.org.au>
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