## processes #### csci 3410 | spring 2023 #### Prof. Sibin Mohan

tackling complexity

  • modern computers → 100s of programs
  • programs can interfere with each other
  • complex!



abstractions!

### isolation
### isolation - one program **cannot** interfere with another
### isolation - one program **cannot** interfere with another - core provision of modern OSes and architectures

process

process

- process ID pid

- memory acessible only to process

  [code, global data, stack, heap]

- integer descriptors that identify resources

  [file system, networking, communication]

- current working directory pwd

- owner sibin

- parent → creator, responsible for it

- arguments passed from command line

- environment variables → system config information

### Unix Philosophy
### Unix Philosophy - programs should be **simple**
### Unix Philosophy - programs should be **simple** - **should not** be large monolithic pieces of code
### Unix Philosophy - programs should be **simple** - **should not** be large monolithic pieces of code - "doing one thing well" - e.g., `ls`, `ps`, `pwd`, etc.
### Unix Philosophy - programs should be **simple** - **should not** be large monolithic pieces of code - "doing one thing well" - e.g., `ls`, `ps`, `pwd`, etc. - **pipelines** of processes
### Unix Philosophy - programs should be **simple** - **should not** be large monolithic pieces of code - "doing one thing well" - e.g., `ls`, `ps`, `pwd`, etc. - **pipelines** of processes - `$ ps aux | grep sibin`
### `fork()`
### `fork()` Create a new, child, process
### `fork()` Create a new, child, process from the **state of the calling process**
##### process creation/termination/coordination API
##### process creation/termination/coordination API - `fork` → create process
##### process creation/termination/coordination API - `fork` → create process - `getpid` → get ID of process
##### process creation/termination/coordination API - `fork` → create process - `getpid` → get ID of process - `getppid` → get ID of parent
##### process creation/termination/coordination API - `fork` → create process - `getpid` → get ID of process - `getppid` → get ID of parent - `exit` → terminate a process
##### process creation/termination/coordination API - `fork` → create process - `getpid` → get ID of process - `getppid` → get ID of parent - `exit` → terminate a process - `wait` → parent waiting for child to exit
##### process creation/termination/coordination API - `fork` → create process - `getpid` → get ID of process - `getppid` → get ID of parent - `exit` → terminate a process - `wait` → parent waiting for child to exit - `exec` → new program from _current process_
### process vs program
### process vs program - program → **compiled** version of code - process → program **executing** in memory
### `pid_t fork(void)` unistd.h