Re: BASH question: executing a cmd with a pipe that is in a variable
On Tuesday, Aug 9th 2005 at 15:13 -0400, quoth Larry Cook: =I'm being stupid! Can someone please help? = =I've got a BASH script with the following: = =CMD=zcat myfile | tar xf - =$CMD = =This puts zcat's output to stdout, rather than piping it to tar like I want. =Now I'm sure this is how it *should* work. :-( Unfortunately, I can't figure =out how to get it to work like I want. You've already gotten the solution to use the eval command. But I thought it would be instructional to 'splain it so you know why. Look at this example and it becomes more obvious. foo='echo hello | cat' if you say $foo you're expecting to see a hello. Instead you correctly see hello | cat i.e., what you're really getting is this echo 'hello | cat' which makes it perfectly obvious what's happening. If you really want the command to be executed you need an eval to prevent the myfile | tar xf - to all not be args 1 through 5 to zcat. Sounds logical to a Vulcan... -- Time flies like the wind. Fruit flies like a banana. Stranger things have .0. happened but none stranger than this. Does your driver's license say Organ ..0 Donor?Black holes are where God divided by zero. Listen to me! We are all- 000 individuals! What if this weren't a hypothetical question? steveo at syslang.net ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
BASH question: executing a cmd with a pipe that is in a variable
I'm being stupid! Can someone please help? I've got a BASH script with the following: CMD=zcat myfile | tar xf - $CMD This puts zcat's output to stdout, rather than piping it to tar like I want. Now I'm sure this is how it *should* work. :-( Unfortunately, I can't figure out how to get it to work like I want. Thanks, Larry ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: BASH question: executing a cmd with a pipe that is in a variable
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Larry Cook wrote: | I'm being stupid! Can someone please help? | | I've got a BASH script with the following: | | CMD=zcat myfile | tar xf - $CMD You want eval $CMD. | This puts zcat's output to stdout, rather than piping it to tar | like I want. Now I'm sure this is how it *should* work. :-( | Unfortunately, I can't figure out how to get it to work like I | want. | | Thanks, Larry ___ | gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org | http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.1 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFC+QMb/TBScWXa5IgRAgzRAJ9PtQgS0fleT2oKzQJPGNPBCn7oMwCeMjnn QSjEvIb2nvDUlMDVrCyYJmM= =1VpX -END PGP SIGNATURE- ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: BASH question: executing a cmd with a pipe that is in a variable
Bruce, Thanks for the quick response and simple solution. Larry Bruce Dawson wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Larry Cook wrote: | I'm being stupid! Can someone please help? | | I've got a BASH script with the following: | | CMD=zcat myfile | tar xf - $CMD You want eval $CMD. | This puts zcat's output to stdout, rather than piping it to tar | like I want. Now I'm sure this is how it *should* work. :-( | Unfortunately, I can't figure out how to get it to work like I | want. | | Thanks, Larry ___ | gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org | http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.1 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFC+QMb/TBScWXa5IgRAgzRAJ9PtQgS0fleT2oKzQJPGNPBCn7oMwCeMjnn QSjEvIb2nvDUlMDVrCyYJmM= =1VpX -END PGP SIGNATURE- ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: BASH question: executing a cmd with a pipe that is in a variable
Larry Cook writes: I'm being stupid! Can someone please help? I've got a BASH script with the following: CMD=zcat myfile | tar xf - $CMD This puts zcat's output to stdout, rather than piping it to tar like I want. This is because the shell's order of operations is different than what you think it is. The man pages describes this in gory detail. Now I'm sure this is how it *should* work. :-( Unfortunately, I can't figure out how to get it to work like I want. You could either just invoke zcat myfile | tar xf - directly (but I guess you have some reason why you can't do that) or else you could just try eval $CMD. Hope this helps, --kevin -- GnuPG ID: B280F24E And the madness of the crowd alumni.unh.edu!kdc Is an epileptic fit -- Tom Waits ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: bash question
On Mon, 23 Sep 2002 [EMAIL PROTECTED] wrote: In a message dated: Mon, 23 Sep 2002 11:37:40 EDT Thomas M. Albright said: If the due date is greater than today, it outputs the message Due in x days. If the due date is less than today I get a message saying You are -x days past due. How can I convert the negative number into a positive one in bash? Well, assuming that 'x' is a variable which contains some whole number representing the number of days in which 'it' is due, a negative number representing an over-due 'it', then: abs_x=`echo '$x' | sed s/-//` ought to do it. Yay! Thanks! -- TARogue (Linux user number 234357) You can always tell a Texan, but you can't tell him much. - Chris Wall ___ gnhlug-discuss mailing list [EMAIL PROTECTED] http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: bash question
On Mon, 23 Sep 2002, Thomas M. Albright wrote: =I don't have any of my bash scripting books handy so I figured I'd ask =here: I have a script that checks due dates. I use `date +%j` to convert =both today and the date due into day of year. (eg - today is 266) I then =subtract today from the due date. = =If the due date is greater than today, it outputs the message Due in x =days. If the due date is less than today I get a message saying You =are -x days past due. How can I convert the negative number into a =positive one in bash? daysPastDue=$((daysPastDue * -1)) -- -Time flies like the wind. Fruit flies like a banana. Stranger things have - -happened but none stranger than this. Does your driver's license say Organ -Donor?Black holes are where God divided by zero. Listen to me! We are all- -individuals! What if this weren't a hypothetical question? [EMAIL PROTECTED] ___ gnhlug-discuss mailing list [EMAIL PROTECTED] http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
