how to open stdout - comp.lang.c

<boss_bhat@yahoo.co.in> wrote in message news:1126162198.682281.208370@z14g2000cwz.googlegroups.com... > Assume stdout is closed and if i now > want to open stdout, how to open it? Don't close it. ("Doctor, when I do it it hurts.", "Don't do it.") > IS this correct way of opening stdout > > fopen(stdout,"/dev/null"); Oh my goodness... Alex

<boss_bhat@yahoo.co.in> wrote in message news:1126169469.388158.125330@g47g2000cwa.googlegroups.com... > please somebody explain me how to open STDOUT? It's already open upon entry to main(). Just don't close it and you'll be OK. Alex

boss_bhat@yahoo.co.in wrote: > Assume stdout is closed and if i now > want to open stdout, how to open it? Don't close it. If it is closed : int fd; fd = open("/dev/tty", O_WRONLY); stdout = fdopen(fd, "w"); This code depends on UNIX, since closing / opening any of the standard streams is probably undefined :) > IS this correct way of opening stdout > > fopen(stdout,"/dev/null"); Depends. If you actually want to use data send to stdout : no. If you don't care : yes Igmar

boss_bhat@yahoo.co.in wrote: # Assume stdout is closed and if i now # want to open stdout, how to open it? # # IS this correct way of opening stdout # # fopen(stdout,"/dev/null"); Don't. Use freopen("/dev/null","w",stdout) instead. -- SM Ryan http://www.rawbw.com/~wyrmwif/ She broke your heart and inadvertently drove men to deviant lifestyles.

On Thu, 08 Sep 2005 00:01:41 -0700, boss_bhat wrote: > Assume stdout is closed and if i now > want to open stdout, how to open it? If it is closed you can't portably reopen it in C. > IS this correct way of opening stdout > > fopen(stdout,"/dev/null"); No, fopen() takes a pointer to a string specifying a file name as its first argument, and one specifying a mode as its second. What you can do is change the file stdout is open to using the freopen() function: freopen("/dev/null", "w", stdout) The 3rd argument must be an existing open stream for this to be valid, so just make sure you don't close stdout if you want to do this. Lawrence

SM Ryan <wyrmwif@tango-sierra-oscar-foxtrot-tango.fake.org> wrote: >boss_bhat@yahoo.co.in wrote: ># Assume stdout is closed and if i now ># want to open stdout, how to open it? ># ># IS this correct way of opening stdout ># ># fopen(stdout,"/dev/null"); > >Don't. Use > freopen("/dev/null","w",stdout) >instead. 1. I know of several systems that don't know anything about /dev/null. 2. On the ones that do, writing to /dev/null is usually not the same as writing to whatever-stdout-happened-to-point-to on program startup. 3. Calling freopen with a third parameter that does not currently point to a stream invokes undefined behaviour (AFAIK). To OP: Simply don't close stdout, if you want to make further use of it. Best regards -- Irrwahn Grausewitz (irrwahn35@freenet.de) welcome to clc : http://www.ungerhu.com/jxh/clc.welcome.txt clc faq-list : http://www.faqs.org/faqs/C-faq/faq/ clc frequent answers: http://benpfaff.org/writings/clc.

"Alexei A. Frounze" wrote: > > <boss_bhat@yahoo.co.in> wrote in message > news:1126169469.388158.125330@g47g2000cwa.googlegroups.com... > > please somebody explain me how to open STDOUT? > > It's already open upon entry to main(). Just don't close it and you'll be > OK. And if you need to associate stdout with something else for whatever reason, check out freopen(). -- +-------------------------+--------------------+-----------------------------+ | Kenneth J. Brody | www.hvcomputer.com | | | kenbrody/at\spamcop.net | www.fptech.com | #include <std_disclaimer.h> | +-------------------------+--------------------+-----------------------------+ Don't e-mail me at: <mailto:ThisIsASpamTrap@gmail.com>

Igmar Palsenberg wrote: > > boss_bhat@yahoo.co.in wrote: > > Assume stdout is closed and if i now > > want to open stdout, how to open it? > > Don't close it. If it is closed : > > int fd; > > fd = open("/dev/tty", O_WRONLY); > stdout = fdopen(fd, "w"); stdout isn't an l-value. [...] -- +-------------------------+--------------------+-----------------------------+ | Kenneth J. Brody | www.hvcomputer.com | | | kenbrody/at\spamcop.net | www.fptech.com | #include <std_disclaimer.h> | +-------------------------+--------------------+-----------------------------+ Don't e-mail me at: <mailto:ThisIsASpamTrap@gmail.com>

Kenneth Brody wrote: >>Don't close it. If it is closed : >> >>int fd; >> >>fd = open("/dev/tty", O_WRONLY); >>stdout = fdopen(fd, "w"); > > > stdout isn't an l-value. Depends. On this system, it is. On systems where stdout is a macro, you're in trouble. If that's the case : stick with freopen() Igmar

Igmar Palsenberg wrote: > > Kenneth Brody wrote: > > >>Don't close it. If it is closed : > >> > >>int fd; > >> > >>fd = open("/dev/tty", O_WRONLY); > >>stdout = fdopen(fd, "w"); > > > > > > stdout isn't an l-value. > > Depends. On this system, it is. On systems where stdout is a macro, > you're in trouble. If that's the case : stick with freopen() "It may be an l-value on some systems" == "It's not a l-value as far as clc is concerned". :-) Of course, one could make a similar argument about "/dev/tty". -- +-------------------------+--------------------+-----------------------------+ | Kenneth J. Brody | www.hvcomputer.com | | | kenbrody/at\spamcop.net | www.fptech.com | #include <std_disclaimer.h> | +-------------------------+--------------------+-----------------------------+ Don't e-mail me at: <mailto:ThisIsASpamTrap@gmail.com>

In article <43213155$0$11076$e4fe514c@news.xs4all.nl>, Igmar Palsenberg <igmar@jdimedia.local> wrote: >Kenneth Brody wrote: >> stdout isn't an l-value. >Depends. On this system, it is. On systems where stdout is a macro, >you're in trouble. C89 -defines- stdout as being a macro. It might happen that the expansion of the macro gives you something that could be used as an l-value, but you shouldn't count on that. A common Unix value for stdout is the local equivilent of &__iob[1] -- "Who Leads?" / "The men who must... driven men, compelled men." "Freak men." "You're all freaks, sir. But you always have been freaks. Life is a freak. That's its hope and glory." -- Alfred Bester, TSMD