system-calls

read and sysread have very similar documentation. What are the differences between the two? About read : read supports PerlIO layers. read works with any Perl file handle [1] . read buffers. read obtains data from the system in fixed sized blocks of 8 KiB [2] . read may block if less data than requested is available [3] . About sysread : sysread doesn't support PerlIO layers (meaning it requires a raw a.k.a. binary handle). sysread only works with Perl file handles that map to a system file handle/descriptor [4] . sysread doesn't buffer. sysread performs a single system call. sysread returns

here is the code(exit.s): .section .data, .section .text, .globl _start _start: movl $1, %eax movl $32, %ebx syscall when I execute " as exit.s -o exit.o && ld exit.o -o exit -e _start && ./exit" the return is "Bus error: 10" and the output of " echo $? " is 138 I also tried the example of the correct answer in this question: Process command line in Linux 64 bit stil get "bus error"... First, you are using old 32-bit Linux kernel calling convention on Mac OS X - this absolutely doesn't work. Second, syscalls in Mac OS X are structured in a different way - they all have a leading class

On Linux (or Solaris) is there a better way than hand parsing /proc/self/maps repeatedly to figure out whether or not you can read, write or execute whatever is stored at one or more addresses in memory? For instance, in Windows you have VirtualQuery . In Linux, I can mprotect to change those values, but I can't read them back. Furthermore, is there any way to know when those permissions change (e.g. when someone uses mmap on a file behind my back) other than doing something terribly invasive and using ptrace on all threads in the process and intercepting any attempt to make a syscall that