Re: [Fwd: [PATCH] arithmetic - logical shift]
Chet Ramey wrote: Pádraig Brady wrote: Original Message Date: Tue, 07 Oct 2008 11:55:51 +0100 From: Pádraig Brady [EMAIL PROTECTED] To: Chet Ramey [EMAIL PROTECTED] CC: [EMAIL PROTECTED] I was just discussing bit shifting with Tim Hockin using shell arithmetic expansion, and he pointed out that bash and ksh use arithmetic rather than logical shift for the operator. Actually, bash and ksh use whatever the native C compiler implements, since both just translate the and into the same operators internally. I don't see a really compelling reason to change, since, as you say, the standard requires signed long ints. Well that means the result is compiler dependent. So scripts could give different results on another platform, or less often within a platform. Also arithmetic right shift is not useful. Pádraig.
Re: Interrupted system call when piping to grep
Tanel Rebane wrote: Hello, a problem occurs when running the following bash shell script: #!/usr/bin/env bash for (( q = 0 ; q 1 ; q++ )); do while read -d '' z; do result+=($z); done (printf %s\000\n hej | grep -a 'hej') done For some reason the following output is printed: ./test.bash: line 4: /var/tmp//sh-np-2094024698: Interrupted system call ./test.bash: line 4: /var/tmp//sh-np-1952491205: Interrupted system call ./test.bash: line 4: /var/tmp//sh-np-2936939995: Interrupted system call ./test.bash: line 4: /var/tmp//sh-np-255058020: Interrupted system call etc etc... This seems to only happen when piping to grep. I'm using FBSD 6.2-STABLE, Bash 3.2.33(0)-release and grep (GNU grep) 2.5.1-FreeBSD. I took a look at this, and it's not just due to the grep. I think it's a timing problem, but I can't tell what signal is interrupting the open. I thought it might be SIGCHLD, but I don't think so now. It just seems that FreeBSD's named pipe implementation is a bit fragile. Chet -- ``The lyf so short, the craft so long to lerne.'' - Chaucer Chet Ramey, ITS, CWRU[EMAIL PROTECTED]http://cnswww.cns.cwru.edu/~chet/
implementing flow control in bash
Hello all, I'm sure this isn't a bug, but just my inability to wrap my head around enough of bash flow control: I wrote the following shell script to find all gifs in a directory. Then use identify from imagemagick to grab the gif width. Then, print the image name and width to a file. for i in `find . -name \*gif`; do identify -format $i %w $i; done results.txt Then, I used a ruby script to cull only those images with a width over 570 pixels. So, problem solved, but I wanted to see if I could do it all in bash. More specifically, (if this makes sense) I want to do identify -format $i %w $i only for those $i %w where %w is 570. The above script will give me output like: image1.gif 360 image2.gif 780 But I want it to give me: image1.gif 360 In pseudo-code, I want something like: for i in `find . -name \*gif`; do identify -format $i %w $i if [%w 570]; done results.txt Any suggestions? Tony
Re: implementing flow control in bash
Tony Zanella schrieb: Hello all, I'm sure this isn't a bug, but just my inability to wrap my head around enough of bash flow control: I wrote the following shell script to find all gifs in a directory. Then use identify from imagemagick to grab the gif width. Then, print the image name and width to a file. for i in `find . -name \*gif`; do identify -format $i %w $i; done results.txt Then, I used a ruby script to cull only those images with a width over 570 pixels. So, problem solved, but I wanted to see if I could do it all in bash. More specifically, (if this makes sense) I want to do identify -format $i %w $i only for those $i %w where %w is 570. The above script will give me output like: image1.gif 360 image2.gif 780 But I want it to give me: image1.gif 360 In pseudo-code, I want something like: for i in `find . -name \*gif`; do identify -format $i %w $i if [%w 570]; done results.txt for i in $(find -name '*.gif') do w=$(identify -format %w $i) (( w 570 )) echo $i $w done Hope that helps, Bernd -- Bernd Eggink http://sudrala.de
