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Full Discussion: Bash statement equivalent
Top Forums UNIX for Dummies Questions & Answers Bash statement equivalent Post 302921358 by Corona688 on Thursday 16th of October 2014 02:47:45 PM
Old 10-16-2014
I'm not sure this ever did quite what you thought. It could certainly change the perceived order of stdout/stderr. The two different, separate tees are liable to stomp on each other's lines. And this may interfere with redirections run outside the script, too. It's only a strange concidence of how bash works that gives this the appearance of working under some circumstances, but it also did weird things like catching prompts...

Potentially changing the order stdout/stderr come in order is inevitable when doing this, and doing this reliably is always cumbersome since it's supposed to be done from the outside.

This is the shortest "reliable" one I've yet seen managed:

Code:
#!/bin/ksh

log=ksh.log

rm -f $log /tmp/$$-e /tmp/$$-o /tmp/$$-m
mkfifo /tmp/$$-o /tmp/$$-e /tmp/$$-m || exit 1

(       tee /tmp/$$-m /dev/tty < /tmp/$$-o & # will wait for exec >
        tee /tmp/$$-m /dev/tty < /tmp/$$-e & # will wait for exec 2>
        cat < /tmp/$$-m > $log &             # will wait for $$-m
        ) >/dev/null

exec > /tmp/$$-o        # First tee will start running
exec 2>/tmp/$$-e        # Second tee will start running
while [ ! -e "$log" ] ; do true ; done
rm -f /tmp/$$-o /tmp/$$-e /tmp/$$-m

echo "stdout stuff"
echo "stderr stuff">&2

There's shorter/simpler versions using tail -f, to just print the output file instead of catching it midway, but it's possible for them to skip output and hang, not to mention all your output ends up going to stdout. The worst this one will do is reorder stderr/stdout and possibly print a line on your prompt after it quits -- unfortunately inevitable unless you're prepared to make a lot of guarantees about what your code will and won't be doing with traps and stdin/stdout/stderr. Right now this shouldn't interfere with those.
Last edited by Corona688; 10-16-2014 at 03:56 PM..
 

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LEARN ABOUT OPENSOLARIS

getusershell

getusershell(3C)					   Standard C Library Functions 					  getusershell(3C)

NAME

       getusershell, setusershell, endusershell - get legal user shells

SYNOPSIS

       #include <unistd.h>

       char *getusershell(void);

       void setusershell(void);

       void endusershell(void);

DESCRIPTION

       The  getusershell()  function  returns  a  pointer  to  a  legal  user  shell  as defined by the system manager in the file /etc/shells. If
       /etc/shells does not exist, the following locations of the standard system shells are used in its place:

	 /bin/bash		    /bin/csh
	 /bin/jsh		    /bin/ksh
	 /bin/ksh93		    /bin/pfcsh
	 /bin/pfksh		    /bin/pfsh
	 /bin/sh		    /bin/tcsh
	 /bin/zsh		    /sbin/jsh
	 /sbin/pfsh		    /sbin/sh
	 /usr/bin/bash		    /usr/bin/csh
	 /usr/bin/jsh		    /usr/bin/ksh
	 /usr/bin/ksh93 	    /usr/bin/pfcsh
	 /usr/bin/pfksh 	    /usr/bin/pfsh
	 /usr/bin/sh		    /usr/bin/tcsh
	 /usr/bin/zsh		    /usr/sfw/bin/zsh
	 /usr/xpg4/bin/sh

       The getusershell() function opens the file /etc/shells, if it exists, and returns the next entry in the list of shells.

       The setusershell() function rewinds the file or the list.

       The endusershell() function closes the file, frees any memory used by getusershell() and setusershell(), and rewinds the file /etc/shells.

RETURN VALUES

       The getusershell() function returns a null pointer on EOF.

BUGS

       All information is contained in memory that may be freed with a call to endusershell(), so it must be copied if it is to be saved.

NOTES

       Restricted shells should not be listed in /etc/shells.

SunOS 5.11							    1 Nov 2007							  getusershell(3C)
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