Intermediate C Programming

8 Intermediate C Programming

• You need to write a program that produces correct outputs based on given inputs.

This is frequently the case when taking programming courses. The correctness of the

program is evaluated by whether your program produces correct outputs. In many

cases, the programs are graded by computer programs based on the input-output

pairs. In this case, nobody reads the information on a computer screen.

If > and a ﬁle name is added after the command, then the output is saved in that ﬁle.

$ ./prog abc 123 C Programs > output

Nothing appears on the computer screen because the information is redirected to the

ﬁle whose name is output. You can use a text editor to see the contents of this ﬁle. You

can also use the Linux command more or less or cat to see the ﬁle’s content. If you type

more output in the terminal, this is what appears on the computer screen:

main: a = 5, b = 17, argc = 5

Since the output is saved in a ﬁle, you can use the diff command to check whether

that output is the same as the correct output, assuming you have the correct output saved

in another ﬁle. The diff command requires the names of two ﬁles and determines whether

these ﬁles are the same or not. If they are diﬀerent, the command shows the line-by-line

diﬀerences. The diff program will compare the ﬁles exactly. It is often useful to ignore

whitespace and this can be done by adding -w after diff. Adding -q after diff shows only

whether the ﬁles are diﬀerent or not, without showing the line-by-line diﬀerences. Although

the diff command is useful, sometimes we want to see the diﬀerences side-by-side. The

meld program in Linux does precisely that.

Table of Contents for Intermediate C Programming