Re: [Rd] Reading exit code of pipe()
The difference in the return value of close(pipeConnectionObject) seems to depend on whether the pipe connection was opened via the pipe() or open() functions (close() returns NULL) con - pipe(ls) open(con, r) readLines(con, n=1) [1] 1032.R print(close(con)) NULL con - pipe(ls, r) scan(con, n=1, what=) Read 1 item [1] 1032.R print(close(con)) NULL or via something like readLines() or scan() (close() returns status integer). con - pipe(ls) scan(con, n=1, what=) Read 1 item [1] 1032.R print(close(con)) [1] 36096 sprintf(0x%x, .Last.value) [1] 0x8d00 Bill Dunlap TIBCO Software wdunlap tibco.com On Wed, May 13, 2015 at 10:27 PM, Kevin Ushey kevinus...@gmail.com wrote: Hi Jeroen, I think `pipe` might just be returning the status code of the underlying command executed; for example, I get a status code of '0' when I test a pipe on `ls`: conn - pipe(ls) stream - readLines(conn) print(close(conn)) Similarly, I get an error code if I try to `ls` a non-existent directory (512 in my case), e.g. conn - pipe(ls /no/path/here/sir) stream - readLines(conn) print(close(conn)) So maybe `cat` just doesn't set a status code, and so there's nothing for R to forward back (ergo -- NULL)? Kevin On Wed, May 13, 2015 at 5:24 PM, Jeroen Ooms jeroen.o...@stat.ucla.edu wrote: Is there a way to get the status code of a pipe() command? The documentation suggests that it might be returned by close, however this does not seem to be the case. con - pipe(cat /etc/passwd, r) stream - readLines(con, n = 10) err - close(con) print(err) __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel [[alternative HTML version deleted]] __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] Reading exit code of pipe()
On Thu, May 14, 2015 at 1:27 AM, Kevin Ushey kevinus...@gmail.com wrote: [...] So maybe `cat` just doesn't set a status code, and so there's nothing for R to forward back (ergo -- NULL)? cat definitely sets the status. IMHO every command sets the exit status, by definition, at least on Unix/Linux. /tmp$ touch x /tmp$ cat x /tmp$ echo $? 0 /tmp$ cat y cat: y: No such file or directory /tmp$ echo $? 1 Gabor [...] [[alternative HTML version deleted]] __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] Reading exit code of pipe()
On Thu, May 14, 2015 at 7:30 AM, William Dunlap wdun...@tibco.com wrote: The difference in the return value of close(pipeConnectionObject) seems to depend on whether the pipe connection was opened via the pipe() or open() functions (close() returns NULL) or via something like readLines() or scan() (close() returns status integer). Hmm interesting. It doesn't help me though; the connection has to be explicitly opened to support streaming otherwise it keeps running the command over and over again: con - pipe(ls -ltr /) readLines(con, n = 3) readLines(con, n = 3) readLines(con, n = 3) isOpen(con) Under the hood, R distinguishes closing and destroying the connection. The R function close actually means destroy. It seems like the pipe exit code is only properly returned if the connection was already closed but not destroyed by the time close() was called. __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] Reading exit code of pipe()
Not sure if it helps for your use case, but I have an experimental package for controlling bidirectional pipe streams from R. Just thought I'd mention it. Its at https://github.com/thk686/pipestreamr THK On Thu, May 14, 2015 at 9:30 AM, William Dunlap wdun...@tibco.com wrote: The difference in the return value of close(pipeConnectionObject) seems to depend on whether the pipe connection was opened via the pipe() or open() functions (close() returns NULL) con - pipe(ls) open(con, r) readLines(con, n=1) [1] 1032.R print(close(con)) NULL con - pipe(ls, r) scan(con, n=1, what=) Read 1 item [1] 1032.R print(close(con)) NULL or via something like readLines() or scan() (close() returns status integer). con - pipe(ls) scan(con, n=1, what=) Read 1 item [1] 1032.R print(close(con)) [1] 36096 sprintf(0x%x, .Last.value) [1] 0x8d00 Bill Dunlap TIBCO Software wdunlap tibco.com On Wed, May 13, 2015 at 10:27 PM, Kevin Ushey kevinus...@gmail.com wrote: Hi Jeroen, I think `pipe` might just be returning the status code of the underlying command executed; for example, I get a status code of '0' when I test a pipe on `ls`: conn - pipe(ls) stream - readLines(conn) print(close(conn)) Similarly, I get an error code if I try to `ls` a non-existent directory (512 in my case), e.g. conn - pipe(ls /no/path/here/sir) stream - readLines(conn) print(close(conn)) So maybe `cat` just doesn't set a status code, and so there's nothing for R to forward back (ergo -- NULL)? Kevin On Wed, May 13, 2015 at 5:24 PM, Jeroen Ooms jeroen.o...@stat.ucla.edu wrote: Is there a way to get the status code of a pipe() command? The documentation suggests that it might be returned by close, however this does not seem to be the case. con - pipe(cat /etc/passwd, r) stream - readLines(con, n = 10) err - close(con) print(err) __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel [[alternative HTML version deleted]] __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel -- Timothy H. Keitt http://www.keittlab.org/ [[alternative HTML version deleted]] __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] Reading exit code of pipe()
Hi Jeroen, I think `pipe` might just be returning the status code of the underlying command executed; for example, I get a status code of '0' when I test a pipe on `ls`: conn - pipe(ls) stream - readLines(conn) print(close(conn)) Similarly, I get an error code if I try to `ls` a non-existent directory (512 in my case), e.g. conn - pipe(ls /no/path/here/sir) stream - readLines(conn) print(close(conn)) So maybe `cat` just doesn't set a status code, and so there's nothing for R to forward back (ergo -- NULL)? Kevin On Wed, May 13, 2015 at 5:24 PM, Jeroen Ooms jeroen.o...@stat.ucla.edu wrote: Is there a way to get the status code of a pipe() command? The documentation suggests that it might be returned by close, however this does not seem to be the case. con - pipe(cat /etc/passwd, r) stream - readLines(con, n = 10) err - close(con) print(err) __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
