Alias or command to compile and link all C files

Question

I recently started compiling/linking my C files by hand using the gcc command. However it requires all of the source files to be typed at the end of the command. When there are many files to compile/link it can be boring. That's why I had the idea of making a bash alias for the command which would directly type all *.h and *.c files of the folder.

My line in .bashrc is this:

alias compile='ls *.c *.h | gcc -o main'

I found it to work some times but most of the time compile will return this :

gcc: fatal error: no input files

compilation terminated.

I thought that pipe would give the results of ls *.c *.h as arguments to gcc but it doesn't seem to work that way. What am I doing wrong? Is there a better way to achieve the same thing?

Thanks for helping

Answer 1

A pipe does not create command line arguments. A pipe feeds standard input.

You need xargs to convert standard input to command line arguments.

But you don't need (or want) xargs or ls or standard input here at all.

If you just want to compile every .c file into your executable then just use:

gcc -o main *.c

(You don't generally need .h files on gcc command lines.)

As Kay points out in the comments the pedantically correct and safer version of the above command is (and I don't intend this in a pejorative fashion):

gcc -o main ./*.c

See Filenames and Pathnames in Shell: How to do it Correctly for an extensive discussion of the various issues here.

That being said you can use any of a number of tools to save you from needing to do this and from needing to rebuild everything when only some things change.

Tools like make or its many clones, "front-ends" (eg the autotools, cmake) or replacements (tup, scons, cons, and about a million other tools).

Answer 2

Have you tried using a makefile ? It sounds like that might be more efficient for what you're trying to do.

If you really want to do it with BASH aliases, you have to use xargs to get standard input to command line arguments.

Answer 3

There are several misconceptions here:

• the pipe redirects the standard output of the first command to the standard input of the second command; however, gcc doesn't accept the files to compile on stdin, but on the command line;
• the wildcard syntax is not something that is magical just to ls , it's the shell that performs their expansion on the command line;
• header files are not to be compiled - you compile .c files, which in turn may include headers.

Armed with this knowledge, you'll understand that the correct command something like

gcc -o main *.c

Actually we can do better: first of all, you'll want to change the *.c to ./*.c ; this prevents files whose name start with a - from being interpreted as command line options.

Most importantly, you should really enable the compiler warnings, they can be life saver. You'll want to add -Wall and -Wextra .

gcc -Wall -Wextra -o main ./*.c

Finally, it's worth saying that by default you are compiling with optimizations disabled. If you are debugging that's OK, but you want also to add -g to have an executable usable in debugging; otherwise, if the target is speed you should at least add -O2 .