进程的 pid、ppid、uid、euid、gid 和 egid 之间有什么区别？
What is the difference between a Process' pid, ppid, uid, euid, gid and egid?
上下文：我正在获取当前 Ruby 进程 ID。
Process.pid #=> 95291
Process.ppid #=> 95201
Process.uid #=> 501
Process.gid #=> 20
Process.euid #=> 501
Process.egid #=> 20
顺序：
pid: 是你调用Process.pid方法的进程的进程号(PID)。ppid：父进程（产生当前进程的进程）的 PID。例如，如果您在 bash shell 中 运行 ruby test.rb，则该进程中的 PPID 将是 Bash 的 PID。 uid：进程所在的用户的 UNIX ID 运行ning。 euid：进程 运行ning 所属的 有效 用户 ID。 EUID 根据允许使用此 UID 的用户执行的操作来确定允许程序执行的操作。通常与 uid 相同，但可能与 sudo 等命令不同。 gid：程序 运行ning 所在的 UNIX 组 ID。egid：类似于 euid，但适用于群组。
PID:
In Linux, an executable stored on disk is called a program, and a program loaded into memory and running is called a process. When a process is started, it is given a unique number called process ID (PID) that identifies that process to the system. If you ever need to kill a process, for example, you can refer to it by its PID.
PPID:
In addition to a unique process ID, each process is assigned a parent process ID (PPID) that tells which process started it. The PPID is the PID of the process’s parent.
For example, if process1 with a PID of 101 starts a process named process2, then process2 will be given a unique PID, such as 3240, but it will be given the PPID of 101. It’s a parent-child relationship. A single parent process may spawn several child processes, each with a unique PID but all sharing the same PPID.
UID:
Unix-like operating systems identify users within the kernel by a value called a user identifier, often abbreviated to UID or User ID. The UID, along with the GID and other access control criteria, is used to determine which system resources a user can access. The password file maps textual usernames to UIDs, but in the kernel, only UID's are used.
EUID:
The effective UID (euid) of a process is used for most access checks. It is also used as the owner for files created by that process.
GID:
A group identifier, often abbreviated to GID, is a numeric value used to represent a specific group. The range of values for a GID varies amongst different systems; at the very least, a GID can be between 0 and 32,767, with one restriction: the login group for the superuser must have GID 0.
EGID:
The effective GID (egid) of a process also affects access control and may also affect file creation, depending on the semantics of the specific kernel implementation in use and possibly the mount options used.
有关详细信息，请参阅这些文章：
- What are PID and PPID?
- Meaning of PID, PPID and TGID
- User identifier
- Group identifier
除了上述综合答案外，我还想分享一些 linux 命令和相应的输出，这可能有助于实现 real 和 [=19] 之间的区别=]effective user id/group for current logged in user myuser:
真实用户名和组名以及数字 ID
$ id
uid=1000(myuser) gid=1000(myuser) groups=1000(myuser),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),119(lpadmin),130(lxd),131(sambashare)
有效的用户名和组名以及数字 ID
$ sudo id
uid=0(root) gid=0(root) groups=0(root)
上下文：我正在获取当前 Ruby 进程 ID。
Process.pid #=> 95291
Process.ppid #=> 95201
Process.uid #=> 501
Process.gid #=> 20
Process.euid #=> 501
Process.egid #=> 20
顺序：
pid: 是你调用Process.pid方法的进程的进程号(PID)。ppid：父进程（产生当前进程的进程）的 PID。例如，如果您在 bash shell 中 运行ruby test.rb，则该进程中的 PPID 将是 Bash 的 PID。uid：进程所在的用户的 UNIX ID 运行ning。euid：进程 运行ning 所属的 有效 用户 ID。 EUID 根据允许使用此 UID 的用户执行的操作来确定允许程序执行的操作。通常与uid相同，但可能与sudo等命令不同。gid：程序 运行ning 所在的 UNIX 组 ID。egid：类似于euid，但适用于群组。
PID:
In Linux, an executable stored on disk is called a program, and a program loaded into memory and running is called a process. When a process is started, it is given a unique number called process ID (PID) that identifies that process to the system. If you ever need to kill a process, for example, you can refer to it by its PID.
PPID:
In addition to a unique process ID, each process is assigned a parent process ID (PPID) that tells which process started it. The PPID is the PID of the process’s parent.
For example, if process1 with a PID of 101 starts a process named process2, then process2 will be given a unique PID, such as 3240, but it will be given the PPID of 101. It’s a parent-child relationship. A single parent process may spawn several child processes, each with a unique PID but all sharing the same PPID.
UID:
Unix-like operating systems identify users within the kernel by a value called a user identifier, often abbreviated to UID or User ID. The UID, along with the GID and other access control criteria, is used to determine which system resources a user can access. The password file maps textual usernames to UIDs, but in the kernel, only UID's are used.
EUID:
The effective UID (euid) of a process is used for most access checks. It is also used as the owner for files created by that process.
GID:
A group identifier, often abbreviated to GID, is a numeric value used to represent a specific group. The range of values for a GID varies amongst different systems; at the very least, a GID can be between 0 and 32,767, with one restriction: the login group for the superuser must have GID 0.
EGID:
The effective GID (egid) of a process also affects access control and may also affect file creation, depending on the semantics of the specific kernel implementation in use and possibly the mount options used.
有关详细信息，请参阅这些文章：
- What are PID and PPID?
- Meaning of PID, PPID and TGID
- User identifier
- Group identifier
除了上述综合答案外，我还想分享一些 linux 命令和相应的输出，这可能有助于实现 real 和 [=19] 之间的区别=]effective user id/group for current logged in user myuser:
真实用户名和组名以及数字 ID
$ id
uid=1000(myuser) gid=1000(myuser) groups=1000(myuser),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),119(lpadmin),130(lxd),131(sambashare)
有效的用户名和组名以及数字 ID
$ sudo id
uid=0(root) gid=0(root) groups=0(root)