Whats is the behaviour of the "wc" command?

Question

For example:

myCleanVar=$( wc -l < myFile )
myDirtVar=$( wc -l myFile )

echo $myCleanVar
9

echo $myDirtVar
9 myFile

why in "myCleanVar" I get an "integer" value from the "wc" command and in "myDirtVar" I get something like as: "9 file.txt"? I quoted "integer" because in know that in Bash shell by default all is treated as a string, but can't understand the differences of the behaviour of first and second expression. What is the particular effect of the redirection "<" in this case?

Answer 1

wc will list by default the name of file allowing you to use it on more than one file (and have result for all of them). If no filename is specified, the "standard input", which is usually the console input, is used, and no file name is printed. The < is needed to specify an "input redirection", that is read the input from given file instead of using user input.

Put all this information together and you get the reason of wc's behavior in your example

Question time: what would be the output of cat file | wc -l ?