stdin

How can I tell if STDIN is connected to a terminal in Perl? if (-t STDIN) { # stdin is connected } else { # stdin is not connected } I usually use this in conjunction with -t STDOUT, to find out if I'm running from an interactive shell, or from cron, to enable more output. You might also be interested in IO::Interactive to figure out if Perl thinks it is interacting with a user. Simply being connected to a tty doesn't mean the user is going to see what you do. One solution would be to use tty: [root@server] ~> tty /dev/pts/0 [root@server] ~> echo y | tty not a tty But not very pretty... 来源：

I'm writing my first Perl app -- an AOL Instant Messenger bot that talks to an Arduino microcontroller, which in turn controls a servo that will push the power button on our sysadmin's server, which freezes randomly every 28 hours or so. I've gotten all the hard stuff done, I'm just trying to add one last bit of code to break the main loop and log out of AIM when the user types 'quit'. The problem is, if I try to read from STDIN in the main program loop, it blocks the process until input is entered, essentially rendering the bot inactive. I've tried testing for EOF before reading, but no dice.

Is there a way to provide the code to Rscript -e in multiple lines? This is possible in vanilla R R --vanilla <<code a <- "hello\n" cat(a) code But using Rscript I get two different things depending on the R version. # R 3.0.2 gives two ignores Rscript -e ' quote> a <- 3+3 quote> cat(a, "\n") quote> ' # ARGUMENT 'cat(a,~+~"' __ignored__ # ARGUMENT '")' __ignored__ Rscript -e 'a <- 3+3;cat(a, "\n")' # ARGUMENT '")' __ignored__ # R 2.15.3 gives an ignore for the multiline, but it works with semicolons Rscript -e ' quote> a <- 3+3 quote> cat(a, "\n") quote> ' # ARGUMENT 'cat(a,~+~"\n")' __ignored

I want to know how to check if my input buffer(perhaps its called stdin) is empty or not. i dont want the program to stop if the buffer is empty, and i dont want the input to necessarily end with '\n', therefore just using scanf is not enough. i tried searching on google and on this website but no answer was enough. i tried using feof(stdin) like this: int main() { char c,x; int num; scanf("%c",&c); scanf("%c",&x); num=feof(stdin); printf("%d",num); } but all it did was printing 0 no matter the input. adding fflush(stdin) after the second scanf gave the same result. other answers suggested

I want my ksh script to have different behaviors depending on whether there is something incoming through stdin or not: (1) cat file.txt | ./script.ksh (then do "cat <&0 >./tmp.dat" and process tmp.dat) vs. (2) ./script.ksh (then process $1 which must be a readable regular file) Checking for stdin to see if it is a terminal[ -t 0 ] is not helpful, because my script is called from an other script. Doing "cat <&0 >./tmp.dat" to check tmp.dat's size hangs up waiting for an EOF from stdin if stdin is "empty" (2nd case). How to just check if stdin is "empty" or not?! vladr EDIT: You are running on