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On 09/08/2022 21:01, Roger L Costello wrote: Yet the Unix 'file' [1] command has been doing a pretty good job of itA file has no inherent format. The format of a file is determined by the programs that use it. Since file types are not determined by the file system, the "kernel" can't tell you the type of file: it doesn't know. since 1973. [2] The 'file' command firstly uses filesystem tests to determine if a file is empty or is a special file, such as a socket or a symbolic link. It secondly uses 'magic' tests to detect the file type. The 'file' manpage includes: The magic tests are used to check for files with data in particular fixed formats. The magic tests use "magic patterns" from a 'magic' file. [3] The 'magic' file on my Linux system includes 11 patterns that start with '<?xml'. They are mostly followed by other tests to try to determine the type of XML, e.g.: 0 string \<?xml\ version=" >15 string >\0 >>19 search/4096 \<svg SVG Scalable Vector Graphics image There's even a test for '<?XML' that will be reported as 'broken XML document'. Regards, Tony Graham. -- Senior Architect XML Division Antenna House, Inc. ---- Skerries, Ireland tgraham@a... [1] https://www.man7.org/linux/man-pages/man1/file.1.html [2] https://www.man7.org/linux/man-pages/man1/file.1.html#HISTORY [3] https://man7.org/linux/man-pages/man4/magic.4.html
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