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Re: Possible ZSH bug with IO direction
- X-seq: zsh-workers 38320
- From: Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>
- To: roger.qiu@xxxxxxxxx, zsh-workers@xxxxxxx
- Subject: Re: Possible ZSH bug with IO direction
- Date: Sat, 23 Apr 2016 15:14:36 -0700
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On Apr 24, 4:30am, Roger Qiu wrote:
}
} > gm convert -compress JPEG - - < input.jpg > output.jpg
} gm convert: Corrupt JPEG data: 873 extraneous bytes before marker 0xd9
} (/tmp/gmo1fx92).
I suspect you are encountering the issue that "gm" wants input.jpg in
binary mode, but zsh's input redirection operator has forced it to text
mode. A lengthy comment in Src/main.c (copypasted below) explains this.
There's [intended to be] an easy workaround, which is to open the file
for both read and write even though you're only going to read it:
gm convert -compress JPEG - - <> input.jpg > output.jpg
However, it's been years since I had a Cygwin system or the time/patience
to care to set one up, so I haven't tested the workaround.
Aside: The zsh/system module "sysopen" doesn't recognize O_BINARY or
O_TEXT modes; that should probably be corrected if someone can compile
on a system that has them, but of course the comment below indicates
that O_BINARY would be overridden anyway.
* Peter A. Castro <doctor@xxxxxxxxxxxx>
*
* Cygwin supports the notion of binary or text mode access to files
* based on the mount attributes of the filesystem. If a file is on
* a binary mounted filesystem, you get exactly what's in the file, CRLF's
* and all. If it's on a text mounted filesystem, Cygwin will strip out
* the CRs. This presents a problem because zsh code doesn't allow for
* CRLF's as line terminators. So, we must force all open files to be
* in text mode reguardless of the underlying filesystem attributes.
* However, we only want to do this for reading, not writing as we still
* want to write files in the mode of the filesystem. To do this,
* we have two options: augment all {f}open() calls to have O_TEXT added to
* the list of file mode options, or have the Cygwin runtime do it for us.
* I choose the latter. :)
*
* Cygwin's runtime provides pre-execution hooks which allow you to set
* various attributes for the process which effect how the process functions.
* One of these attributes controls how files are opened. I've set
* it up so that all files opened RDONLY will have the O_TEXT option set,
* thus forcing line termination manipulation. This seems to solve the
* problem (at least the Test suite runs clean :).
*
* Note: this may not work in later implementations. This will override
* all mode options passed into open(). Cygwin (really Windows) doesn't
* support all that much in options, so for now this is OK, but later on
* it may not, in which case O_TEXT will have to be added to all opens calls
* appropriately.
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