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Top Forums Shell Programming and Scripting Redirecting standard out to /dev/null goes to file "/dev/null" instead Post 302598442 by jbmorrisonjr on Tuesday 14th of February 2012 12:30:50 PM
Old 02-14-2012
Thank you chihung for the fix.

So let me see if I understand this. I need to play tokenizer in my head to see this.

The parser sees the redirect token and sees that it is followed by a substitution string instead of something else like a directory path. Tokenizing on white-space (with parphrasing) it sees
... <stdout-redirect-append> <substitution-string>
instead of
... <stdout-redirect-append> <file-path> <stderr-redirect> <to-whereever-stdout-goes>

the <substitution-string> is internally processed as a <file-path> and since most characters, including spaces, can be in file names, the file name is "null 2>&1".

Subtle. A second parsing, after all string substitution would have reworked it, hence "eval".

Did I kinda get this right?

Thanks
John Morrison
 

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SHCOMP(1)						       Korn shell utilities							 SHCOMP(1)

NAME
shcomp - compile a shell script SYNOPSIS
shcomp [ options ] [infile [outfile]] DESCRIPTION
Unless -D is specified, shcomp takes a shell script, infile, and creates a binary format file, outfile, that ksh can read and execute with the same effect as the original script. Since aliases are processed as the script is read, alias definitions whose value requires variable expansion will not work correctly. If -D is specified, all double quoted strings that are preceded by $ are output. These are the messages that need to be translated to locale specific versions for internationalization. If outfile is omitted, then the results will be written to standard output. If infile is also omitted, the shell script will be read from standard input. OPTIONS
[D dictionary] Generate a list of strings that need to be placed in a message catalog for internationalization. [n noexec] Displays warn- ing messages for obsolete or non-conforming constructs. [v verbose] Displays input from infile onto standard error as it reads it. EXIT STATUS
0 Successful completion. >0 An error occurred. SEE ALSO
ksh(1) IMPLEMENTATION
version shcomp (AT&T Research) 2003-03-02 author David Korn <dgk@research.att.com> copyright Copyright (c) 1982-2010 AT&T Intellectual Property license http://www.opensource.org/licenses/cpl1.0.txt 2003-03-02 SHCOMP(1)
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