Truss with the -p switch can be used to begin tracing of a process which has been running, without having to start it over. This is useful when a suspect program runs for a while and gives an indication or condition that a crash or problem is imminent output of some kind, for example.
For example, suppose a program runs for several minutes, and then gives a certain output shortly before it terminates abnormally. Truss will provide a clue as to what happens to cause the program to terminate abnormally, without having to accumulate output during the first several minutes of operation.
Output of truss can be restricted to a given set of system service calls using the -t switch. This, too, can help cut down on the amount of output to wade through in finding an answer, assuming the user knows what to look for. Generally, when a program terminates abnormally but does not crash, it is because a system service call returned an error. This may be due to a programming error, or may be due to circumstance.
Truss can help determine the cause of the problem. Truss can also help debug where a program crashed by providing a trace of the system service calls up until the crash. This output, plus source code, can help determine where the program crashed.
Is there a way to redirect output to a file and have it display on stdout? Improve this question. Mike 2 2 silver badges 14 14 bronze badges. If someone just ended up here looking for capturing error output to file, take a look at - unix. That is, writing to the file is writing to stdout. You are asking if it is possible to write both to stdout and to the terminal. WilliamPursell I'm not sure your clarification improves things :- How about this: OP is asking if it's possible to direct the called program's stdout to both a file and the calling program's stdout the latter being the stdout that the called program would inherit if nothing special were done; i.
And maybe they also want to direct the called program's stderr similarly "any output from that command" might be reasonably interpreted to mean including stderr. Add a comment. Active Oldest Votes. The command you want is named tee : foo tee output.
Furthermore, if you want to append to the log file, use tee -a as: program [arguments Improve this answer. Zoredache Zoredache There certainly are conditions where you might not want stderr as part of the output being saved to a file. When I answered this 5 years ago I assumed that the OP only wanted stdout, since he mentioned stdout in the subject of the post. Ah sorry, I might have been a little confused. When I tried it I just got no output, perhaps it was all going to stderr.
Use -a argument on tee to append content to output. Show 14 more comments. Matthew Alpert Matthew Alpert 5, 1 1 gold badge 14 14 silver badges 13 13 bronze badges. Anyone know of an 'unbuffer' for osx? If you're using OS X, it's marginally easier to use unbuffer in most cases, although not if you want to pass signals to the command you're running.
Sometimes you might want to redirect the output of one command as input to another command. A set of commands strung together in this way is called a pipeline. The symbol for this type of redirection is a vertical bar called a pipe. We hate spam too, unsubscribe at any time. Table of Contents. Subscribe on YouTube!
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