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Shell Programming and Scripting
How to auto correct a failing command?
Post 302989990 by Corona688 on Friday 20th of January 2017 10:38:48 AM
01-20-2017
He hasn't said so explicitly, but I've gained the impression that mohtashims has been required to maintain and port a lot of shell scripts not all his own devising, and hopes for cookie-cutter solutions for scripts written using non-portable options.
There a few strategies you can try.
Solution #1 obviously looks easier and more attractive, since hypothetically it can be done with just a "header" section and few to no changes to large amounts of code you may not necessarily understand. But if it really was better, you would have solved your problems months ago. You must be dealing with a large number of very different systems, as you're still finding and plugging hole after hole, and will continue to do so for a long time. What will you do when you hit one which doesn't have GNU extensions available?
Solution #2 is a big job. I've spent large amounts of time duplicating one command.
Solution #3 unfortunately means having to understand what grep -o actually means, so as to replace it. You may want to break it down and test commands individually rather than fighting it as one gigantic block of code.
My last comment: This is what happens when you try and detect and compensate for every difference between systems:
That's 800 kilobytes of ad-hoc corrections per decade, more or less.
There a few strategies you can try.
- Substituting different commands on different systems.
- Building your own substitutes for every troublesome command.
- Re-factoring the scripts to use actually portable options.
Solution #1 obviously looks easier and more attractive, since hypothetically it can be done with just a "header" section and few to no changes to large amounts of code you may not necessarily understand. But if it really was better, you would have solved your problems months ago. You must be dealing with a large number of very different systems, as you're still finding and plugging hole after hole, and will continue to do so for a long time. What will you do when you hit one which doesn't have GNU extensions available?
Solution #2 is a big job. I've spent large amounts of time duplicating one command.
Solution #3 unfortunately means having to understand what grep -o actually means, so as to replace it. You may want to break it down and test commands individually rather than fighting it as one gigantic block of code.
My last comment: This is what happens when you try and detect and compensate for every difference between systems:
That's 800 kilobytes of ad-hoc corrections per decade, more or less.
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img-tiff
img-tiff(n) img-tiff(n) NAME
img-tiff - Img, Tagged Image File Format (tiff) SYNOPSIS
package require Tk package require img::tiff ?1.3? image create photo ?name? ?options? DESCRIPTION
The package img::tiff is a sub-package of Img. It can be loaded as a part of the complete Img support, via package require Img, or on its own, via package require img::tiff. Like all packages of Img it does not provide new commands, but extends the existing Tk command image so that it supports files containing raster images in the Tagged Image File Format (tiff). More specifically img::tiff extends Tk's photo image type. The name of the new format handler is tiff. This handler provides new additional configuration options. See section TIFF OPTIONS for more detailed explanations. All of the above means that in a call like image create photo ?name? ?options? [1] Image data in tiff format (options -data and -file) is detected automatically. [2] The format name tiff is recognized by the option -format. In addition the value for the option is treated as list and may contain any of the special options listed in section TIFF OPTIONS. TIFF OPTIONS
The handler provides two options to influence the writing of a TIFF image. There are no options to influence the reader. -compression type This option specifies the type of compression to use when writing TIFF data. It has to be one of none, jpeg, packbits, or deflate. The default is none. -byteorder type This option specifies the byteorder to use when writing TIFF data. It has to be one of bigendian, littleendian, network, smallen- dian, or the empty string. The default is the empty string. The values bigendian and network are aliases of each other, as are littleendian and smallendian. SEE ALSO
img-bmp, img-gif, img-ico, img-intro, img-jpeg, img-pcx, img-pixmap, img-png, img-ppm, img-ps, img-sgi, img-sun, img-tga, img-tiff, img- window, img-xbm, img-xpm KEYWORDS
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