Software & Apps Linux Learn the Linux Command Open This system call converts path names into file descriptors by Juergen Haas Writer Former Lifewire writer Juergen Haas is a software developer, data scientist, and a fan of the Linux operating system. our editorial process Juergen Haas Updated on February 23, 2020 DigiPub / Getty Images Linux Switching from Windows Tweet Share Email The open() system call linux command converts a pathname into a file descriptor—a small, non-negative integer for use in subsequent I/O as with read, write, etc. When the call is successful, the file descriptor returned will be the lowest file descriptor not currently open for the process. This call creates a new open file, not shared with any other process. This system call isn't a command. It's a function used in programming and scripting. Most desktop Linux hobbyists who aren't programmers will never use this system call.