NAME

lprof − display line-by-line execution count profile data

SYNOPSIS

lprof [−p] [−s] [−x] [−I incdir] [−r srcfile] [−c cntfile] [−o prog] [−V]

lprof −m file1.cnt file2.cnt filen.cnt [−T] −d destfile.cnt

DESCRIPTION

lprof reports the execution characteristics of a program on a (source) line by line basis.  This is useful as a means to determine which and how often portions of the code were executed. 

lprof interprets a profile file (prog.cnt by default) produced by the profiled program prog (a.out by default).  prog creates a profile file if it has been loaded with the −ql option of cc.  The profile information is computed for functions in a source file if the −ql option was used when the source file was compiled. 

A shared object may also be profiled by specifying −ql when the shared object is created.  When a dynamically linked executable is run, one profile file is produced for each profiled shared object linked to the executable.  This feature is useful in building a single report covering multiple and disparate executions of a common library.  For example, if programs prog1 and prog2 both use library libx.a, running these profiled programs will produce two profile files, prog1.cnt and prog2.cnt, which cannot be combined.  However, if libx is built as a profiled shared object, libx.so, and prog1 and prog2 are built as profiled dynamically linked executables, then running these programs with the merge option will produce three profile files; one of them, libx.so.cnt, will contain the libx profile information from both runs. 

By default, lprof prints a listing of source files (the names of which are stored in the symbol table of the executable file), with each line preceded by its line number (in the source file) and the number of times the line was executed. 

The following options may appear singly or be combined in any order:

−p Print listing, each line preceded by the line number and the number of times it was executed (default).  This option can be used together with the −s option to print both the source listing and summary information. 

−s Print summary information of percentage of lines of code executed per function. 

−x Instead of printing the execution count numbers for each line, print each line preceded by its line number and a [U] if the line was not executed.  If the line was executed, print only the line number. 

−I incdir Look for source or header files in the directory incdir in addition to the current directory and the standard place for #include files (usually /usr/include).  The user can specify more than one directory by using multiple −I options. 

−r srcfile Instead of printing all source files, print only those files named in −r options (to be used with the −p option only).  The user can specify multiple files with a single −r option. 

−c cntfile Use the file cntfile instead of prog.cnt as the input profile file. 

−o prog Use the name of the program prog instead of the name used when creating the profile file.  Because the program name stored in the profile file contains the relative path, this option is necessary if the executable file or profile file has been moved. 

−V Print, on standard error, the version number of lprof. 

Merging Data Files

lprof can also be used to merge profile files.  The −m option must be accompanied by the −d option:

−m file1.cnt file2.cnt filen.cnt −d destfile.cnt
Merge the data files file1.cnt through filen.cnt by summing the execution counts per line, so that data from several runs can be accumulated.  The result is written to destfile.cnt.  The data files must contain profiling data for the same prog (see the −T option below). 

−T Time stamp override.  Normally, the time stamps of the executable files being profiled are checked, and data files will not be merged if the time stamps do not match.  If −T is specified, this check is skipped. 

CONTROLLING THE RUN-TIME PROFILING ENVIRONMENT

The environment variable PROFOPTS provides run-time control over profiling.  When a profiled program (or shared object) is about to terminate, it examines the value of PROFOPTS to determine how the profiling data are to be handled.  A terminating shared object will honor every PROFOPTS option except file=filename. 

The environment variable PROFOPTS is a comma-separated list of options interpreted by the program being profiled.  If PROFOPTS is not defined in the environment, then the default action is taken:  The profiling data are saved in a file (with the default name, prog.cnt) in the current directory.  If PROFOPTS is set to the null string, no profiling data are saved.  The following are the available options:

msg=[y|n] If msg=y is specified, a message stating that profile data are being saved is printed to stderr.  If msg=n is specified, only the profiling error messages are printed.  The default is msg=y. 

merge=[y|n]
If merge=y is specified, the data files will be merged after successive runs.  If merge=n is specified, the data files are not merged after successive runs, and the data file is overwritten after each execution.  The merge will fail if the program has been recompiled, and the data file will be left in TMPDIR.  The default is merge=n. 

pid=[y|n] If pid=y is specified, the name of the data file will include the process ID of the profiled program.  Inclusion of the process ID allows for the creation of different data files for programs calling fork.  If pid=n is specified, the default name is used.  The default is pid=n.  For lprof to generate its profiling report, the −c option must be specified with lprof otherwise the default will fail. 

dir=dirname The data file is placed in the directory dirname if this option is specified.  Otherwise, the data file is created in the directory that is current at the end of execution. 

file=filename
filename is used as the name of the data file in dir created by the profiled program if this option is specified.  Otherwise, the default name is used.  For lprof to generate its profiling report, the −c option must be specified with lprof if the file option has been used at execution time; otherwise the default will fail. 

FILES

prog.cnt profile data

TMPDIR usually /var/tmp but can be redefined by setting the environment variable TMPDIR [see tempnam in tmpnam(3S)]. 

SEE ALSO

cc(1), prof(1), fork(2), tmpnam(3S). 

NOTES

For the −m option, if destfile.cnt exists, its previous contents are destroyed. 

Optimized code cannot be profiled; if both optimization and line profiling are requested, profiling has precedence. 

Including header files that contain code (such as stat.h or utsname.h) will cause erroneous data. 

Different parts of one line of a source file may be executed different numbers of times (for example, the for loop below); the count corresponds to the first part of the line. 

For example, in the following for loop

main()
1[2]{
int j;
1[5]for (j = 0; j < 5; j++)
5[6]sub(j);
1[8]}
sub(a)
int a;
5[12]{
5[13]printf("a is %d\n", a);
5[14]}

line 5 consists of three parts. The line count listed, however, is for the initialization part, that is, j = 0. 

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