The following functions return fail if a system error occurred, for
example, if name-file does not exist (except for IsExistingFile). In
this case the function LastSystemError can be used to get information
about the error.
IsExistingFile( name-file ) F
returns true if a file with the filename name-file exists, and
false otherwise.
IsReadableFile( name-file ) F
returns true if a file with the filename name-file exists and the
GAP process has read permissions for the file, and false if it has
no such permissions.
IsWriteableFile( name-file ) F
returns true if a file with the filename name-file exists and the
GAP process has write permissions for the file, and false if it has
no such permissions.
IsExecuteableFile( name-file ) F
returns true if a file with the filename name-file exists and the
GAP process has execute permissions for the file, and false if it
has no such permissions. Note that execute permissions do not imply that it
is possible to execute the file, e.g., it could only be an executable on a
different machine.
IsDirectoryPath( name-file ) F
returns true if the file with the filename name-file exists and is
a directory. It returns false if the file exists but is a plain file.
Note that this functions does not check if the GAP process
actually has write or execute permissions for the directory.
Examples
# the file `/bin/date' exists gap> IsExistingFile( "/bin/date" ); true # the file `/bin/date.new' does not exist gap> IsExistingFile( "/bin/date.new" ); false # `/bin/date' is not a directory gap> IsExistingFile( "/bin/date/new" ); fail gap> LastSystemError().message; "Not a directory" # the file `/bin/date' is readable gap> IsReadableFile( "/bin/date" ); true # the file `/bin/date.new' does not exist gap> IsReadableFile( "/bin/date.new" ); fail gap> LastSystemError().message; "No such file or directory" # the file `/bin/date' is not writable gap> IsWritableFile( "/bin/date" ); false # but executable gap> IsExecutableFile( "/bin/date" ); true
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GAP 4 manual