Zoe, a zoologist in Madagascar, has been saving samples of dung beetles as plain text files in a directory in her laptop. She wants to use the
cat command to show the content of all of the samples in her screen.
cat command can take multiple filenames as arguments, meaning that
cat filename1 filename2 will show the content of both filename1 and filename2.
In order to print the content of all files in the directory by executing the
cat command only once, she could:
- hit three times the Tab key and have the shell autocomplete the cat command with all the filenames
- substitute the filenames with the asterisk symbol
- substitute the filenames with the
/([A-Za-z0-9.])*/gregular expression, which matches all of the filenames in the directory
- type carefully all of the filenames, since there is no other way to do it
Zoe has been naming the samples using the convention: subtribe.genera
The directory includes the following files:
apterepilissus.sericeus helictopleurus.undatus arachnodes.refulgens helictopleurus.viettei arachnodes.pillula helictopleurus.viridiflavus epilissus.splendidus nanos.clypeatus epilissus.ruteri nanos.viettei
Zoe is writing a paper on the arachnodes subtribe and wants to read only the relative samples. The right way to do it is:
Zoe is interested in comparing the samples of the
viettei genera across the nanos and the endemic to Madagascar helictopleurus subtribes. She can do it with a single command:
The right answer to MCQ 2 is… the 3rd one! The first
* gets expanded to all possible strings (in this case to the nanos and helictopleurus subtribes), and the
* at the end matches zero characters.
Unlike the 2nd option, where the
? at the end has to be expanded to at least one character.
The 1st option checks whether the student knows that the
? matches a single character and only one.
Finally, the 4th option makes sure the student does not confuses wildcards with regular expressions.