How to Program in
C,continued...
Troubleshooting
Did your program not run? Let's do some trouble shooting.
First, say over and over again, "I love Unix. I swear I
do! Honest! I love C, too!" Now try to compile and run this
program another way. You start with the same code as before,
which is saved in the file "hello.c". However, this
time, give the command:
cc -o hello hello.c
What this does is:
1) start your C compiler running with the "cc" command
using the -o switch. A quick use of the command "man cc"
tells us that the switch "-o" after the "cc"
tells your compiler to output the compiled version as a file
with the name of your choice.
2) the "hello" part of the command tells the compiler
that this is what you want to name your compiled program
3) with the 'hello.c" part of the command you tell the compiler
where to find the source code you just wrote which you input
into the compiler.
Now -- simply give the command "hello". Your computer
should say back to you, "Hello, hackers!" Congratulations!
You are now a C programmer.
Still doesn't work? Try giving the command "chmod 700
hello". STILL doesn't work? This is a long shot, but maybe
it will solve your problem. If your shell account is set up like
mine, no program can execute from the home directory. It's a
precaution I take against Trojans. (Imagine this, sometimes meanies
put surprises in my account.) However, I have a directory named
"bin" in my account. Normally on Unix systems we name
directories that hold programs "bin". On my account,
that's where I put the programs I write. So look for a directory
"bin" under the home directory in your shell account.
If it doesn't exist, create it with the command "mkdir bin".
Don't forget to give the command "chmod 700 ~/bin"
afterwards! Move "hello" into it with the command "mv
hello bin/hello".
STILL DOESN'T WORK??? Here's the bad news. There are so many
kinds of Unix, and so many shells to interpret your commands,
and so many ways to configure Unixes -- I may not be able to
solve your problem. As the C bible that we like to call simply
"K&R" (The
C Programming Language by Kernighan and Ritchie) warns, "Just
how to run this program depends on the system you are using."
So don't phone or email me for help. Call tech support at
your ISP! That's what you are paying them for, right? They WILL
get your C program working -- if they allow users to compile
C programs. You may even make friends with the tech support guy
you call, as it is really rare and usually makes tech support
guys happy when a customer asks a programming question instead
of the usual lame stuff.
However, before calling tech support, maybe you had better
rewrite your program first to say "Hello, world" instead
of "Hello, hackers!" just in case the tech guy you
talk to is paranoid enough to kick you off for trying to be a
hacker.
More on C --->>
