Re: [gentoo-user] /usr/bin/[ and coreutils
What about [[? I've seen scripts using [[ instead of only one [. Whats the point/difference?
Re: [gentoo-user] /usr/bin/[ and coreutils
On Nov 8, 2011 9:02 AM, Claudio Roberto França Pereira spide...@gmail.com wrote: What about [[? I've seen scripts using [[ instead of only one [. Whats the point/difference? AFAIK [[ was originally a bash-specific built-in command that provides more functionality than /bin/[, but can still use /bin/['s convoluted syntax. The two converged quickly, though. IIRC [ is now also a bash built-in, which still maintains compatibility with /bin/[ An example: [ $VAR ] will produce an error if VAR is empty or unset, but [[ $VAR ]] won't. (for the former, you have to put double quotes around, e.g., [ $VAR] ) Rgds,
Re: [gentoo-user] /usr/bin/[ and coreutils
On Nov 8, 2011 1:01 PM, Pandu Poluan pa...@poluan.info wrote: On Nov 8, 2011 9:02 AM, Claudio Roberto França Pereira spide...@gmail.com wrote: What about [[? I've seen scripts using [[ instead of only one [. Whats the point/difference? AFAIK [[ was originally a bash-specific built-in command that provides more functionality than /bin/[, but can still use /bin/['s convoluted syntax. The two converged quickly, though. IIRC [ is now also a bash built-in, which still maintains compatibility with /bin/[ An example: [ $VAR ] will produce an error if VAR is empty or unset, but [[ $VAR ]] won't. (for the former, you have to put double quotes around, e.g., [ $VAR] ) Uh... of course there should be a space between the second double-quote and the closing bracket. Rgds,
Re: [gentoo-user] /usr/bin/[ and coreutils
Yes, it's a different binary, and it's perfectly usual to find it in a Linux system. But note that, at least in bash, you rarely will be using /usr/bin/[ unless you reference it using the full path (either in a relative or absolute way). This is because bash has a builtin that takes over that binary file. You can check that (or any other command) by using the type instruction (again, this is for bash). # LC_ALL=C type [ [ is a shell builtin The same goes for 'test'. Those binaries are probably there just in case that some init or system script written for a standard bourne shell (like the busybox one) needs it. But don't take my word for it. I am not sure right now. -- Jesús Guerrero Botella
Re: [gentoo-user] /usr/bin/[ and coreutils
On Thu, 13 Oct 2011 15:38:08 +0200 Jesús J. Guerrero Botella jesus.guerrero.bote...@gmail.com wrote: Yes, it's a different binary, and it's perfectly usual to find it in a Linux system. But note that, at least in bash, you rarely will be using /usr/bin/[ unless you reference it using the full path (either in a relative or absolute way). This is because bash has a builtin that takes over that binary file. You can check that (or any other command) by using the type instruction (again, this is for bash). # LC_ALL=C type [ [ is a shell builtin The same goes for 'test'. Those binaries are probably there just in case that some init or system script written for a standard bourne shell (like the busybox one) needs it. But don't take my word for it. I am not sure right now. You might not be sure, but that doesn't stop you still being correct :-) The binaries are usually POSIX-compliant, whereas the builtins may include extra bashisms (which tend to break apps expecting just the basic POSIX behaviour) -- Alan McKinnnon alan.mckin...@gmail.com
Re: [gentoo-user] /usr/bin/[ and coreutils
On Thu, Oct 13, 2011 at 9:50 AM, Alan McKinnon alan.mckin...@gmail.com wrote: On Thu, 13 Oct 2011 15:38:08 +0200 Jesús J. Guerrero Botella jesus.guerrero.bote...@gmail.com wrote: Yes, it's a different binary, and it's perfectly usual to find it in a Linux system. But note that, at least in bash, you rarely will be using /usr/bin/[ unless you reference it using the full path (either in a relative or absolute way). This is because bash has a builtin that takes over that binary file. You can check that (or any other command) by using the type instruction (again, this is for bash). # LC_ALL=C type [ [ is a shell builtin The same goes for 'test'. Those binaries are probably there just in case that some init or system script written for a standard bourne shell (like the busybox one) needs it. But don't take my word for it. I am not sure right now. You might not be sure, but that doesn't stop you still being correct :-) The binaries are usually POSIX-compliant, whereas the builtins may include extra bashisms (which tend to break apps expecting just the basic POSIX behaviour) I haven't encountered POSIX-dependent apps breaking on bash, but I have encountered the reverse. My most annoying experience was when I tried building cinelerra on Debian a few years back. Cinelerra's script started with #!/bin/sh, but depended on bashisms--and I was running dash. -- :wq
Re: [gentoo-user] /usr/bin/[ and coreutils
On Thu, 13 Oct 2011 09:59:21 -0400 Michael Mol mike...@gmail.com wrote: The binaries are usually POSIX-compliant, whereas the builtins may include extra bashisms (which tend to break apps expecting just the basic POSIX behaviour) I haven't encountered POSIX-dependent apps breaking on bash, but I have encountered the reverse. My most annoying experience was when I tried building cinelerra on Debian a few years back. Cinelerra's script started with #!/bin/sh, but depended on bashisms--and I was running dash. So you've also run into clueless devs and maintainers who know almost nothing about shells? Your example is an extreme one :-), but it's common enough to find bashisms in scripts with an sh shebang -- Alan McKinnnon alan.mckin...@gmail.com
Re: [gentoo-user] /usr/bin/[ and coreutils
On Wed, 2011-10-12 at 07:45 +0200, meino.cra...@gmx.de wrote: William Kenworthy bi...@iinet.net.au [11-10-12 07:40]: I have been checking my system for some deep seated problems and in the process, ran across the fact that equery files sys-apps/coreutils-8.7 shows a file included called /usr/bin/[ - thats right, left square bracket! Is that a bug or if real, what would you use it for? It doesnt seem to be on the file system ... moriah ~ # /usr/bin/[ /usr/bin/[: missing `]' moriah ~ # doesnt show much! BillK Hi Wiiliam, this is a convenient 'abbreviation' or 'alias' for cobnstructs such this one if [ foo ] then bar fi in shell scripting. Most shells have implemented this as a builtin (and 'test' also) though. HTH! Best regards, mcc GAH! - now I remember ... goes back to my basic unix skills (or lack of :) - must be getting old ... Thanks all. BillK
Re: [gentoo-user] /usr/bin/[ and coreutils
Am Tue, 11 Oct 2011 22:42:00 -0700 schrieb Canek Peláez Valdés can...@gmail.com: On Tue, Oct 11, 2011 at 10:35 PM, William Kenworthy bi...@iinet.net.au wrote: I have been checking my system for some deep seated problems and in the process, ran across the fact that equery files sys-apps/coreutils-8.7 shows a file included called /usr/bin/[ - thats right, left square bracket! Is that a bug or if real, what would you use it for? It doesnt seem to be on the file system ... moriah ~ # /usr/bin/[ /usr/bin/[: missing `]' moriah ~ # doesnt show much! Relax. It's an alias for test technically it's not an alias, but different binaries % ls -l /usr/bin/\[ -rwxr-xr-x 1 root root 35096 Jan 20 2011 /usr/bin/[ % ls -l /usr/bin/test -rwxr-xr-x 1 root root 31000 Jan 20 2011 /usr/bin/test built from the same source file coreutils/src/test.c with a #define LBRACKET that mainly changes the behavior of the argument parser in case it is built as [. , so instead of using if test blah; then ... fi in bash, you can use if [ blah ]; then ... fi Just do /usr/bin/[ --help to get an idea. It has been there since I started using Linux, if I remember correctly, many years ago. Regards.
[gentoo-user] /usr/bin/[ and coreutils
I have been checking my system for some deep seated problems and in the process, ran across the fact that equery files sys-apps/coreutils-8.7 shows a file included called /usr/bin/[ - thats right, left square bracket! Is that a bug or if real, what would you use it for? It doesnt seem to be on the file system ... moriah ~ # /usr/bin/[ /usr/bin/[: missing `]' moriah ~ # doesnt show much! BillK
Re: [gentoo-user] /usr/bin/[ and coreutils
On Tue, Oct 11, 2011 at 10:35 PM, William Kenworthy bi...@iinet.net.au wrote: I have been checking my system for some deep seated problems and in the process, ran across the fact that equery files sys-apps/coreutils-8.7 shows a file included called /usr/bin/[ - thats right, left square bracket! Is that a bug or if real, what would you use it for? It doesnt seem to be on the file system ... moriah ~ # /usr/bin/[ /usr/bin/[: missing `]' moriah ~ # doesnt show much! Relax. It's an alias for test, so instead of using if test blah; then ... fi in bash, you can use if [ blah ]; then ... fi Just do /usr/bin/[ --help to get an idea. It has been there since I started using Linux, if I remember correctly, many years ago. Regards. -- Canek Peláez Valdés Posgrado en Ciencia e Ingeniería de la Computación Universidad Nacional Autónoma de México
Re: [gentoo-user] /usr/bin/[ and coreutils
On Tue, Oct 11, 2011 at 10:35 PM, William Kenworthy bi...@iinet.net.au wrote: I have been checking my system for some deep seated problems and in the process, ran across the fact that equery files sys-apps/coreutils-8.7 shows a file included called /usr/bin/[ - thats right, left square bracket! Is that a bug or if real, what would you use it for? It doesnt seem to be on the file system ... moriah ~ # /usr/bin/[ /usr/bin/[: missing `]' moriah ~ # doesnt show much! '/usr/bin/[' is a synonym for the '/usr/bin/test' utility. It's used in shell scripts like if [ -f /etc/passwd ] ; then ... So don't worry. It's supposed to be there. -- Manuel A. McLure WW1FA man...@mclure.org http://www.mclure.org ...for in Ulthar, according to an ancient and significant law, no man may kill a cat. -- H.P. Lovecraft
Re: [gentoo-user] /usr/bin/[ and coreutils
William Kenworthy bi...@iinet.net.au [11-10-12 07:40]: I have been checking my system for some deep seated problems and in the process, ran across the fact that equery files sys-apps/coreutils-8.7 shows a file included called /usr/bin/[ - thats right, left square bracket! Is that a bug or if real, what would you use it for? It doesnt seem to be on the file system ... moriah ~ # /usr/bin/[ /usr/bin/[: missing `]' moriah ~ # doesnt show much! BillK Hi Wiiliam, this is a convenient 'abbreviation' or 'alias' for cobnstructs such this one if [ foo ] then bar fi in shell scripting. Most shells have implemented this as a builtin (and 'test' also) though. HTH! Best regards, mcc
