davidandradeduarte / os-api

OS API - from "How Computers Really Work" book, by Matthew Justice

OS API - from "How Computers Really Work" book, by Matthew Justice

gcc -o newfile newfile.c
./newfile
cat file1.txt

Hello, file!

python3 newfile.py
cat file2.txt

Hello from Python!

Analysing system calls

strace ./newfile

C functions being used are wrappers to these system calls
3 - number of the file descriptor
13 - number of bytes written
0 - success exit code

openat(AT_FDCWD, "file1.txt", O_WRONLY|O_CREAT|O_TRUNC, 0644) = 3
write(3, "Hello, file!\n", 13)          = 13
close(3)

now the python's program

strace python3 newfile.py

the same system calls are being made, with the addition of others, since when running with python we're using the python standard libraries (which may be doing other system calls for other reasons), in addition to the python interpreter also being traced by strace

openat(AT_FDCWD, "file2.txt", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE|O_CLOEXEC, 0666) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
ioctl(3, TCGETS, 0xbedf5070)            = -1 ENOTTY (Inappropriate ioctl for device)
_llseek(3, 0, [0], SEEK_CUR)            = 0
ioctl(3, TCGETS, 0xbedf5040)            = -1 ENOTTY (Inappropriate ioctl for device)
_llseek(3, 0, [0], SEEK_CUR)            = 0
write(3, "Hello from Python!\n", 19)    = 19
close(3)