kvancamp@ardc.arpa (LCWSL) (12/05/85)
Has anyone got a version of the tee command that doesn't buffer the I/O? (When I tee my output from an interactive program, with one destination being stdout, I'd like to see everything as it is printed.) Thanks for your help. Ken Van Camp <kvancamp@pica-lca>
charliem@athena.UUCP (Charlie Mills) (12/10/85)
>Has anyone got a version of the tee command that doesn't buffer the I/O?
The standard solution under 4.2BSD is to use tail -f on the output
file. (Don't use tee.) Tail -f doesn't buffer its output between
sleeps. You can kill or suspend the tail without disturbing the
process generating the data. I don't know whether System V has tail or
if so whether there is a -f option or something analogous.
-- Charlie Mills
..{ucbvax,decvax,uw-beaver,hplabs,ihnp4,allegra}!tektronix!athena!charliemkvancamp@ardc.arpa (LCWSL) (12/10/85)
Thanks to all of you who responded to my question about stopping buffering of the tee command (so I could see my output at the same time I echo it to a file). A few suggestions I got were: 1.) Use script. This sounds like it would do the job, but my Masscomp system doesn't have this. 2.) xxx | tee something | cat -u where the -u should force it to be unbuffered. This doesn't seem to work. 3.) Put /dev/null as one of the tee arguments, also to force buffering. I interpreted this as: xxx | tee /dev/null | tee something This, too, doesn't seem to work. The fourth reply I got was from someone who said that what I wanted is impossible because the buffering is inherent in the system (i.e., it isn't the fault of tee because tee already works on only one byte at a time). Does anyone have any other suggestions? Do you know how I can get a copy of script, without violating any copyright laws; or can someone at least point me in the right direction on how to write one? Any help would be appreciated. Please respond directly to me as I do not subscribe to the group. Thanks in advance. Ken Van Camp <kvancamp@pica-lca.arpa>
gnu@l5.uucp (John Gilmore) (12/11/85)
In article <509@brl-tgr.ARPA>, kvancamp@ardc.arpa (LCWSL) writes: > Thanks to all of you who responded to my question about stopping buffering > of the tee command (so I could see my output at the same time I echo it > to a file)...what I wanted is > impossible because the buffering is inherent in the system (i.e., it isn't > the fault of tee... The problem is that a program whose output is a pipe will buffer up a large block of stuff before it writes it to the pipe. If the output is to a terminal, it sends it out as soon as the program writes it. This is done by the standard I/O library to improve performance. Thus if you have xxx | tee file the problem is in stdio in xxx; it's not in "tee". There's no particularly good solution.
chris@umcp-cs.UUCP (Chris Torek) (12/12/85)
In article <509@brl-tgr.ARPA> kvancamp@ardc.arpa (LCWSL) writes: > The fourth reply I got was from someone who said that what I wanted > [`stopping buffering of the tee command'] is impossible because > the buffering is inherent in the system (i.e., it isn't the fault > of tee because tee already works on only one byte at a time). Close. The problem is not in tee, but neither is it in the system: It is in the command you are using on the left hand side of the pipe. Most standard I/O libraries automatically line buffer file output if the file itself is a terminal, and block buffer the output otherwise. A careful program will use `fflush' at appropriate points; indeed, I find that the `helpful' line buffering is unnecessary and even problematical at times. If a program behaves differently---aside of course from speed---when its output is run through an unbuffered `cat'-like filter (e.g., `tee /dev/null'), it is not well written. -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251) UUCP: seismo!umcp-cs!chris CSNet: chris@umcp-cs ARPA: chris@mimsy.umd.edu