“as” is a command in Linux that stands for “assembler.” It is a program that converts assembly language code (a low-level programming language) into machine code that can be executed by a computer.
To use the “as” command, you need to provide it with the name of an assembly language source file as an argument. For example, to assemble a file called “program.s”, you can use the following command:
# as program.s
This will create an object file called “program.o” that contains the machine code version of the assembly language program. You can then use the “ld” (linker) command to combine the object file with other object files and libraries to create an executable file.
For example, to create an executable file called “program” from the object file “program.o”, you can use the following command:
# ld program.o -o program
If you encounter the below error while running the as command:
as: command not found
you may try installing the below package as per your choice of distribution:
| OS Distribution | Command |
|---|---|
| OS X | brew install binutils |
| Debian | apt-get install binutils-i586-linux-gnu |
| Ubuntu | apt-get install binutils-2.26 |
| Alpine | apk add binutils |
| Arch Linux | pacman -S aarch64-linux-gnu-binutils |
| Kali Linux | apt-get install binutils-i686-kfreebsd-gnu |
| CentOS | yum install binutils |
| Fedora | dnf install binutils-arc-linux-gnu |
| Raspbian | apt-get install binutils-mingw-w64-i686 |
as Command Examples
1. Assemble a file, writing the output to a.out:
# as file.s
2. Assemble the output to a given file:
# as file.s -o out.o
3. Generate output faster by skipping whitespace and comment preprocessing. (Should only be used for trusted compilers):
# as -f file.s
4. Include a given path to the list of directories to search for files specified in .include directives:
# as -I path/to/directory file.s