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Full Discussion: Redirecting stdin/stdout to/from command from/to string
Top Forums Shell Programming and Scripting Redirecting stdin/stdout to/from command from/to string Post 302403683 by doc_cypher on Saturday 13th of March 2010 11:11:29 PM
Old 03-14-2010
Question Redirecting stdin/stdout to/from command from/to string
Hi,
I am working on a project where I have to generate and execute nasm code on-the-fly. I generate the code in a file program.asm and then execute it.This output is to stdout which i redirect to an output file which i read back to compare results:
system("nasm -f elf program.asm > output");
The problem is I have to do this process (generate code and execute) a lot of times each time i run my program which slows the execution time due to so much file I/O.

Is there some shell trick by which I can generate my code in a string buffer (instead of the file program.asm) and pass it as input to nasm.
Similarly, can I capture the output of nasm into another string buffer without writing it to a file.

Same applies for compiling c programs using gcc. Can my c program be present in a string which i then compile using gcc by redirecting its input from a file to the string. Likewise, can i redirect the output of my c program to a string instead of stdout or any other file before.
 

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LEARN ABOUT NETBSD

annotate-output

ANNOTATE-OUTPUT(1)					      General Commands Manual						ANNOTATE-OUTPUT(1)

NAME

       annotate-output - annotate program output with time and stream

SYNOPSIS

       annotate-output [options] program [args ...]

DESCRIPTION

       annotate-output will execute the specified program, while prepending every line with the current time and O for stdout and E for stderr.

OPTIONS

       +FORMAT
	      Controls the timestamp format, as per date(1).  Defaults to "%H:%M:%S".

       -h, --help
	      Display a help message and exit successfully.

EXAMPLE

       $ annotate-output make
       21:41:21 I: Started make
       21:41:21 O: gcc -Wall program.c
       21:43:18 E: program.c: Couldn't compile, and took me ages to find out
       21:43:19 E: collect2: ld returned 1 exit status
       21:43:19 E: make: *** [all] Error 1
       21:43:19 I: Finished with exitcode 2

BUGS

       Since  stdout  and  stderr  are	processed  in parallel, it can happen that some lines received on stdout will show up before later-printed
       stderr lines (and vice-versa).

       This is unfortunately very hard to fix with the current annotation strategy.  A fix would involve  switching  to  PTRACE'ing  the  process.
       Giving nice a (much) higher priority over the executed program could however cause this behaviour to show up less frequently.

       The program does not work as well when the output is not linewise.  In particular, when an interactive program asks for input, the question
       might not be shown until after you have answered it.  This will give the impression that the annotated program has hung, while it has not.

SEE ALSO

       date(1)

SUPPORT

       This program is community-supported (meaning: you'll need to fix it yourself).  Patches are however appreciated, as is any feedback  (posi-
       tive or negative).

AUTHOR

       annotate-output	was written by Jeroen van Wolffelaar <jeroen@wolffelaar.nl> This manpage comes under the same copyright as annotate-output
       itself, read /usr/bin/annotate-output (or wherever you install it) for the details.

DEBIAN
								 Debian Utilities						ANNOTATE-OUTPUT(1)
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