1libtracefs(3) 2============= 3 4NAME 5---- 6tracefs_instance_create, tracefs_instance_destroy, tracefs_instance_alloc, tracefs_instance_free, 7tracefs_instance_is_new, tracefs_instances - Manage trace instances. 8 9SYNOPSIS 10-------- 11[verse] 12-- 13*#include <tracefs.h>* 14 15struct tracefs_instance pass:[*]*tracefs_instance_create*(const char pass:[*]_name_); 16int *tracefs_instance_destroy*(struct tracefs_instance pass:[*]_instance_); 17struct tracefs_instance pass:[*]*tracefs_instance_alloc*(const char pass:[*]_tracing_dir_, const char pass:[*]_name_); 18void *tracefs_instance_free*(struct tracefs_instance pass:[*]_instance_); 19bool *tracefs_instance_is_new*(struct tracefs_instance pass:[*]_instance_); 20char pass:[**]*tracefs_instances*(const char pass:[*]_regex_); 21 22-- 23 24DESCRIPTION 25----------- 26This set of functions can be used to manage trace instances. A trace 27instance is a sub buffer used by the Linux tracing system. Given a unique 28name, the events enabled in an instance do not affect the main tracing 29system, nor other instances, as events enabled in the main tracing system 30or other instances do not affect the given instance. 31 32The *tracefs_instance_create()* function allocates and initializes a new 33tracefs_instance structure and returns it. If the instance with _name_ does 34not yet exist in the system, it will be created. The _name_ could be NULL, 35then the new tracefs_instance structure is initialized for the top instance. 36Note that the top instance cannot be created in the system, if it does not 37exist. 38 39The *tracefs_instance_destroy()* removes the instance from the system, but 40does not free the structure. *tracefs_instance_free()* must still be called 41on _instance_. 42 43The tracefs_instance_alloc()* function allocates a new tracefs_instance structure 44for existing trace instance. If the instance does not exist in the system, the function 45fails. The _tracing_dir_ parameter points to the system trace directory. It can be 46NULL, then default system trace directory is used. This parameter is useful to allocate 47instances to trace directories, copied from another machine. The _name_ is the name of 48the instance, or NULL for the top instance in the given _tracing_dir_. 49 50The *tracefs_instance_free()* function frees the tracefs_instance structure, 51without removing the trace instance from the system. 52 53The *tracefs_instance_is_new()* function checks if the given _instance_ is 54newly created by *tracefs_instance_create()*, or it has been in the system 55before that. 56 57The *tracefs_instances*() function returns a list of instances that exist in 58the system that match the regular expression _regex_. If _regex_ is NULL, then 59it will match all instances that exist. The returned list must be freed with 60*tracefs_list_free*(3). Note, if no instances are found an empty list is returned 61and that too needs to be free with *tracefs_list_free*(3). 62 63RETURN VALUE 64------------ 65The *tracefs_instance_create()* and *tracefs_instance_alloc()* functions return a pointer to 66a newly allocated tracefs_instance structure. It must be freed with *tracefs_instance_free()*. 67 68The *tracefs_instance_destroy()* function returns 0 if it succeeds to remove 69the instance, otherwise it returns -1 if the instance does not exist or it 70fails to remove it. 71 72The *tracefs_instance_is_new()* function returns true if the 73*tracefs_instance_create()* that allocated _instance_ also created the 74trace instance in the system, or false if the trace instance already 75existed in the system when _instance_ was allocated by 76*tracefs_instance_create()* or *tracefs_instance_alloc()*. 77 78The *tracefs_instances()* returns a list of instance names that exist on the system. 79The list must be freed with *tracefs_list_free*(3). An empty list is returned if 80no instance exists that matches _regex_, and this needs to be freed with 81*tracefs_list_free*(3) as well. NULL is returned on error. 82 83EXAMPLE 84------- 85[source,c] 86-- 87#include <tracefs.h> 88 89struct tracefs_instance *inst = tracefs_instance_create("foo"); 90 if (!inst) { 91 /* Error creating a new trace instance */ 92 ... 93 } 94 95 ... 96 97 if (tracefs_instance_is_new(inst)) 98 tracefs_instance_destroy(inst); 99 tracefs_instance_free(inst); 100... 101 102struct tracefs_instance *inst = tracefs_instance_alloc(NULL, "bar"); 103 if (!inst) { 104 /* Error allocating 'bar' trace instance */ 105 ... 106 } 107 108 ... 109 110 tracefs_instance_free(inst); 111-- 112FILES 113----- 114[verse] 115-- 116*tracefs.h* 117 Header file to include in order to have access to the library APIs. 118*-ltracefs* 119 Linker switch to add when building a program that uses the library. 120-- 121 122SEE ALSO 123-------- 124*libtracefs*(3), 125*libtraceevent*(3), 126*trace-cmd*(1) 127 128AUTHOR 129------ 130[verse] 131-- 132*Steven Rostedt* <[email protected]> 133*Tzvetomir Stoyanov* <[email protected]> 134-- 135REPORTING BUGS 136-------------- 137Report bugs to <[email protected]> 138 139LICENSE 140------- 141libtracefs is Free Software licensed under the GNU LGPL 2.1 142 143RESOURCES 144--------- 145https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/ 146 147COPYING 148------- 149Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under 150the terms of the GNU Public License (GPL). 151