1LIBTRACEEVENT(3) libtraceevent Manual LIBTRACEEVENT(3)
2
6 tep_register_comm, tep_override_comm, tep_pid_is_registered,
7 tep_data_comm_from_pid, tep_data_pid_from_comm, tep_cmdline_pid -
8 Manage pid to process name mappings.
9
11 #include <event-parse.h>
12 int tep_register_comm(struct tep_handle *tep, const char *comm, int pid);
14 int tep_override_comm(struct tep_handle *tep, const char *comm, int pid);
15 bool tep_is_pid_registered(struct tep_handle *tep, int pid);
16 const char *tep_data_comm_from_pid(struct tep_handle *pevent, int pid);
17 struct cmdline *tep_data_pid_from_comm(struct tep_handle *pevent, const char *comm, struct cmdline *next);
18 int tep_cmdline_pid(struct tep_handle *pevent, struct cmdline *cmdline);
19
21 These functions can be used to handle the mapping between pid and
22 process name. The library builds a cache of these mappings, which is
23 used to display the name of the process, instead of its pid. This
24 information can be retrieved from tracefs/saved_cmdlines file.
25 The tep_register_comm() function registers a pid / process name
27 mapping. If a command with the same pid is already registered, an error
28 is returned. The pid argument is the process ID, the comm argument is
29 the process name, tep is the event context. The comm is duplicated
30 internally.
31 The tep_override_comm() function registers a pid / process name
33 mapping. If a process with the same pid is already registered, the
34 process name string is udapted with the new one. The pid argument is
35 the process ID, the comm argument is the process name, tep is the event
36 context. The comm is duplicated internally.
37 The tep_is_pid_registered() function checks if a pid has a process name
39 mapping registered. The pid argument is the process ID, tep is the
40 event context.
41 The tep_data_comm_from_pid() function returns the process name for a
43 given pid. The pid argument is the process ID, tep is the event
44 context. The returned string should not be freed, but will be freed
45 when the tep handler is closed.
46 The tep_data_pid_from_comm() function returns a pid for a given process
48 name. The comm argument is the process name, tep is the event context.
49 The argument next is the cmdline structure to search for the next pid.
50 As there may be more than one pid for a given process, the result of
51 this call can be passed back into a recurring call in the next
52 parameter, to search for the next pid. If next is NULL, it will return
53 the first pid associated with the comm. The function performs a linear
54 search, so it may be slow.
55 The tep_cmdline_pid() function returns the pid associated with a given
57 cmdline. The tep argument is the event context.
58
60 tep_register_comm() function returns 0 on success. In case of an error
61 -1 is returned and errno is set to indicate the cause of the problem:
62 ENOMEM, if there is not enough memory to duplicate the comm or EEXIST
63 if a mapping for this pid is already registered.
64 tep_override_comm() function returns 0 on success. In case of an error
66 -1 is returned and errno is set to indicate the cause of the problem:
67 ENOMEM, if there is not enough memory to duplicate the comm.
68 tep_is_pid_registered() function returns true if the pid has a process
70 name mapped to it, false otherwise.
71 tep_data_comm_from_pid() function returns the process name as string,
73 or the string "<...>" if there is no mapping for the given pid.
74 tep_data_pid_from_comm() function returns a pointer to a struct
76 cmdline, that holds a pid for a given process, or NULL if none is
77 found. This result can be passed back into a recurring call as the next
78 parameter of the function.
79 tep_cmdline_pid() functions returns the pid for the give cmdline. If
81 cmdline is NULL, then -1 is returned.
82
84 The following example registers pid for command "ls", in context of
85 event tep and performs various searches for pid / process name
86 mappings:
87 #include <event-parse.h>
89 ...
90 int ret;
91 int ls_pid = 1021;
92 struct tep_handle *tep = tep_alloc();
93 ...
94 ret = tep_register_comm(tep, "ls", ls_pid);
95 if (ret != 0 && errno == EEXIST)
96 ret = tep_override_comm(tep, "ls", ls_pid);
97 if (ret != 0) {
98 /* Failed to register pid / command mapping */
99 }
100 ...
101 if (tep_is_pid_registered(tep, ls_pid) == 0) {
102 /* Command mapping for ls_pid is not registered */
103 }
104 ...
105 const char *comm = tep_data_comm_from_pid(tep, ls_pid);
106 if (comm) {
107 /* Found process name for ls_pid */
108 }
109 ...
110 int pid;
111 struct cmdline *cmd = tep_data_pid_from_comm(tep, "ls", NULL);
112 while (cmd) {
113 pid = tep_cmdline_pid(tep, cmd);
114 /* Found pid for process "ls" */
115 cmd = tep_data_pid_from_comm(tep, "ls", cmd);
116 }
117
119 event-parse.h
120 Header file to include in order to have access to the library APIs.
121 -ltraceevent
122 Linker switch to add when building a program that uses the library.
123
125 libtraceevent(3), trace-cmd(1)
126
128 Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent.
129 Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>, author of this man page.
130
132 Report bugs to <linux-trace-devel@vger.kernel.org[3]>
133
135 libtraceevent is Free Software licensed under the GNU LGPL 2.1
136
138 https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/
139
141 1. rostedt@goodmis.org
142 mailto:rostedt@goodmis.org
143 2. tz.stoyanov@gmail.com
145 mailto:tz.stoyanov@gmail.com
146 3. linux-trace-devel@vger.kernel.org
148 mailto:linux-trace-devel@vger.kernel.org
149libtraceevent 1.5.3 07/21/2022 LIBTRACEEVENT(3)