gcc Information

It is possible to edit, compile, run, and debug C programs from solix. The main advantage of this is for people with computers and modems who do not want to purchase Microsoft Visual C++.

Requirements
Compiling and Running Programs
Handing in Programs
Debugging Programs
Deleting files

Requirements

A user account at the school.
If you want to connect from home, then you will also need a computer and modem. You do not need a fancy computer for this, anything will do. The important thing is to have a fast modem. But even this is not necessary, you could use a 300 baud modem (if you still have one), however, screen updates would take a long time.

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So, you want to be a programmer ...

Welcome to the good old days. If you decide to follow this path, then you will need to learn a lot of other stuff than just C++. You will need to know some UNIX related stuff, so check out my UNIX information page. The basic cycle for this process is

Edit your file using an editor of your choice.
Exit the editor, and compile the file from the command prompt using the g++ compiler. The simple command is
gcc -g -o file.out file.c
Where file.out is the name of your output file, and file.cpp is the name of your C source file. You may give these files any name you desire. Issue this command from the UNIX command prompt.
For more complicated programs, you will need to build a make file.
If there are errors, then go back to step 1 and fix them ...
If there are no errors, then you can run your program by typing the name of the output file at the UNIX command prompt.

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Handing in a program

Submitting Homework Online from mongoose or solix I have created a script that you can call from school computers to upload files to my directory. Execute the following from the directory where your C source file is saved on solix:

~downeyt/cs/public/webftp/webftp.pl

and follow the instructions. Use the -h option to learn how to customize the program.

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It runs, but it isn't right ...

There is also a debugger on solix. Actually, there are several. I will describe the gdb debugger, which is a Gnu program.

A debugger allows you to step through a program one line at a time. Here are some of the basic commands for the gdb debugger.

Command Description Abbreviation

gdb file.out This is the command that will start the debugger. file.out is the name of the output file that you created when you compiled your program.

break function
Replace function with the name of any function in your program, including main. When the debugger reaches this function, it will stop and wait for more instructions. b

run
This command starts the debugger. If no break points have been set, then the program will be run to completion. This command can be abbreviated to r.

bt
This is the back trace command. It displays the run time stack.

continue
This command continues program execution. Basically, it is like the run command, except that it starts form the point where the program has been halted. c.

next
Execute the current instruction. If it is a call to a subroutine, then the entire subroutine is executed. The debugger will halt at the next line in the current function. n.

step
Execute the current instruction. If the current instruction is not a call to a subroutine, then step is the same as next. If it is a call to a subroutine, then only call to the subroutine is executed. The debugger will halt at the first line in the subroutine. s

help
On-line help. This command can be abbreviated to h

quit
Exit the debugger. q

list List the current 10 lines of the program l

Command	Description	Abbreviation
`gdb file.out`	This is the command that will start the debugger. file.out is the name of the output file that you created when you compiled your program.
`break function`	Replace function with the name of any function in your program, including main. When the debugger reaches this function, it will stop and wait for more instructions.	b
`run`	This command starts the debugger. If no break points have been set, then the program will be run to completion. This command can be abbreviated to	r.
`bt`	This is the back trace command. It displays the run time stack.
`continue`	This command continues program execution. Basically, it is like the run command, except that it starts form the point where the program has been halted.	c.
`next`	Execute the current instruction. If it is a call to a subroutine, then the entire subroutine is executed. The debugger will halt at the next line in the current function.	n.
`step`	Execute the current instruction. If the current instruction is not a call to a subroutine, then step is the same as next. If it is a call to a subroutine, then only call to the subroutine is executed. The debugger will halt at the first line in the subroutine.	s
`help`	On-line help. This command can be abbreviated to	h
`quit`	Exit the debugger.	q
`list`	List the current 10 lines of the program	l

For more information, issue this command from the UNIX prompt
info -f /depot/gdb-4.15.1/src/gdb/gdb.info

In a typical debug session, you would use the following

break main - tell the debugger to stop when it reaches the main program
run - start executing the program
next - execute the current statement up to the next statement
list - show the contents of the file
continue - run the program to the end, or until the next break

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Deleting files

There is a problem on solix: you don't have a lot of storage space. You will probably only be able to have 1 or 2 executables around at a time. So, if you get a Disk Quota Exceeded message, then you will have to delete some files. Here is how you could delete a file with the name bigfile.ext

rm bigfile.ext

The executables are the largest files, so if you have a problem, delete them first. If you want to keep a copy of them, download them to the A:\ drive before deleting them.

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