cat: Fix reporting "input file is output file" error when outputting to an input file #8025
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could you please add a test to make sure we don't regress? thanks |
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@sylvestre I thought that this PR would make the GNU test These test cases fail: # Initialize files
$ echo x >fx
$ echo x >fx
$ cat fx fy >fxy
$ cat fx >fxy1
$ cat fx >fxy2
# Run `cat` commands
$ cat - fy <fxy1 1<>fxy1
cat: -: input file is output file
$ cat fxy2 fy 1<>fxy2
cat: fxy2: input file is output file
# Test expectations
$ diff fxy fxy1
1d0
< x
$ diff fxy fxy2
1d0
< xThe $ target/debug/cat - fy <fxy1 1<>fxy1
$ diff fxy fxy1
1c1
< x
---
> yI would expect the GNU test to diff the |
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@sylvestre I added the |
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The newer version of GNU |
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The |
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| if !is_same_file_by_path(input, output) { | ||
| return false; | ||
| } | ||
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| // Check if the output file is empty | ||
| FileInformation::from_file(output) | ||
| .map(|info| info.file_size() > 0) | ||
| .unwrap_or(false) |
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I would have liked to do the same thing as with Unix, but unfortunately, the FileInformation objects were not equal when the same file was used as the input and output in Windows. Even their file indexes were different. I could not figure out a simpler way to verify if the files are the same than to use Win32 API to carve the file paths from the handles using GetFinalPathNameByHandleW. I am open to suggestions on a better way to do this.
The corresponding Unix code for a reference:
let Ok(input_info) = FileInformation::from_file(input) else {
return false;
};
let Ok(output_info) = FileInformation::from_file(output) else {
return false;
};
if input_info != output_info || output_info.file_size() == 0 {
return false;
}|
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| /// An unsafe overwrite occurs when the same file is used as both stdin and stdout | ||
| /// and the stdout file is not empty. | ||
| pub fn is_unsafe_overwrite<I: AsHandleRef, O: AsHandleRef>(input: &I, output: &O) -> bool { |
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This function differs from the Unix version in that it does not attempt to determine when a file is safe to be overwritten, namely, when the input handle is pointing to an earlier or the same position of the file as the output handle. I also could not figure out an easy way of determining if the file handle is opened for append, like the O_APPEND flag in Unix.
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great work! :) |
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Remove check if we are appending from stdin to a file. The GNU
catcommand reports the "input file is output file" whenever outputting to a file that was used as input for the command. There are other ways to output to a file than appending.This PR fixes the rest of the test cases from
cat-self.sh:fixes: #7284