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Redirecting stdout continously to a file

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# 1  
Old 06-26-2012
Redirecting stdout continously to a file
I have a C program that continously outputs info to stdout. The problem is that I am redirecting the stdout and stderr to a file and stdout is written at the end of the problem rather than continously to the file. This could be a problem if for example the program is killed and the stdout output is lost. On the other hand, stderr is written continuously to the file.

Thats the way I am doing the redirection of the stdout and stderr.

Code:
c_program > file.log 2>&1

Any ideas how can I redirect the stdout to the file continuously rather than at the end of the program?
Last edited by methyl; 06-26-2012 at 06:40 PM.. Reason: please use code tags
# 2  
Old 06-26-2012
Modify your C program to either disable the buffer for stdout, print a newline more often, or flush its output more often.

stderr and stdout are intended to be separate, however. stdout is for data, stderr is for errors. Why not just print everything you want in the logfile to stdout?
This User Gave Thanks to Corona688 For This Post:
igurov
# 3  
Old 06-26-2012
The behavior you describe is normal. What you probably want is to switch stdout from fully buffered to line buffered (assuming your writes are each terminated by a newline).

Quote:
When a stream is "unbuffered", bytes are intended to appear from the source or at the destination as soon as possible; otherwise, bytes may be accumulated and transmitted as a block. When a stream is "fully buffered", bytes are intended to be transmitted as a block when a buffer is filled. When a stream is "line buffered", bytes are intended to be transmitted as a block when a <newline> byte is encountered. Furthermore, bytes are intended to be transmitted as a block when a buffer is filled, when input is requested on an unbuffered stream, or when input is requested on a line-buffered stream that requires the transmission of bytes. Support for these characteristics is implementation-defined, and may be affected via setbuf() and setvbuf().

...<snip>...

At program start-up, three streams are predefined and need not be opened explicitly: standard input (for reading conventional input), standard output (for writing conventional output), and standard error (for writing diagnostic output). When opened, the standard error stream is not fully buffered; the standard input and standard output streams are fully buffered if and only if the stream can be determined not to refer to an interactive device.
2.5 Standard I/O Streams

Regards,
Alister
This User Gave Thanks to alister For This Post:
igurov
# 4  
Old 06-27-2012
Got it! Thanks a lot!
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