- What are the two file viewing programs that were discussed in the lecture recordings? Specifically list the ones that let you interactively navigate the file.
Two programs we discussed were
more. The two are essentially the same as features have been added to
more over time, so you can use whichever one you like the name of more.
- Suppose we have a program named
MyProgram.javain the current directory. What is the command to run the compiled version of this program and have it read standard input from a file?
java MyProgram < file.txt
Note that we specified that we wanted to run the compiled version. If you wanted to compile and run in one step, you could run
java MyProgram.java < file.txt.
- In your own words, describe the difference between running: and
grep "a" letters.txtWould you expect these two commands to have the same or different output? Why or why not?
cat letters.txt | grep "a"
The output is the same, but how it runs is slightly different.
grep "a" letters.txtuses
letters.txtas a command-line argument
cat letters.txt | grep "a"uses the content of
letters.txt(generated by running the
catcommand) as standard input that the
grepcommand reads from.
This is an important distinction, and we discussed in class how
grep does this by looking at the
SimpleGrep.java program we wrote.
Fill in the blanks below as to what “type” of object should go in each blank based on the type of operations we are performing. For each blank, use options:
filefor a file name
commandfor another command
command | _______ _______ | command command < _______ > _______ command < _______ | _______ command < _______ | _______ > _______
Solutions shown in CAPS
command | COMMAND COMMAND | command command < FILE > FILE command < FILE | COMMAND command < FILE | COMMAND > FILE
- What command would tell us how many files (including hidden files) exist in our parent directory?
ls -a .. | wc -l
- Suppose that I had a file named
MyOtherProgram.javain the current directory. What do you think would happen if I were to run
java MyOtherProgram.java > MyOtherProgram.java?
This tries to run
MyOtherProgram.java and save its output to the file name
MyOtherProgram.java. This means you will overwrite your Java file!