as

Assemble a file, writing output to a.out

$ as [path/to/file.s]

$ as [path/to/file.s] -o [path/to/output.o]

$ as -f [path/to/file.s]

$ as -I [path/to/directory] [path/to/file.s]

as [options] file...

as is the GNU assembler, part of the GNU Binutils collection. It translates assembly language source files into object files that can be linked with ld to create executables.
While primarily intended to assemble output from compilers like gcc, it can also be used directly for low-level programming. The assembler supports multiple target architectures and output formats.

-o file

Write the output object file to file instead of a.out

Fast mode: skip whitespace and comment preprocessing (use only with trusted compiler output)

Add directory to the search path for .include directives

Generate debugging information

Generate 32-bit or 64-bit code (x86)

Suppress warning messages

Assembly syntax varies between architectures. GNU as uses AT&T syntax by default on x86, which differs from Intel syntax. Use .intel_syntax noprefix directive for Intel syntax. The -f flag should only be used with compiler-generated output as it skips syntax validation.

The GNU assembler was developed as part of the GNU project starting in the 1980s. It became part of GNU Binutils and supports virtually all architectures that GCC targets.

gcc(1), ld(1), objdump(1), readelf(1)