Chapter 11

Chapter 11 - Teach Yourself Scheme in Fixnum Days [Go to...

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Teach Yourself Scheme in Fixnum Days [Go to first , previous , next page; contents ; index ] Chapter 11 System interface Useful Scheme programs often need to interact with the underlying operating system. 11.1 Checking for and deleting files file-exists? checks if its argument string names a file. delete-file deletes its argument file. These procedures are not part of the Scheme standard, but are available in most implementations. These procedures work reliably only for files that are not directories. (Their behavior on directories is dialect- specific.) file-or-directory-modify-seconds returns the time when its argument file or directory was last modified. Time is reckoned in seconds from 12 AM GMT, 1 January 1970. Eg, (file-or-directory-modify-seconds "hello.scm") => 893189629 assuming that the file hello.scm was last messed with sometime on 21 April 1998. 11.2 Calling operating-system commands The system procedure executes its argument string as an operating-system command. 4
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Chapter 11 - Teach Yourself Scheme in Fixnum Days [Go to...

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