问题描述
uname -i从哪里获取信息？
/etc/中是否存在详细信息？
/proc/中是否存在详细信息？
如果是这样，则引用哪个文件来输出这些详细信息？
最佳办法
uname使用系统调用uname(2)来获取它显示的与内核相关的信息。
概要是：
#include <sys/utsname.h>
int uname(struct utsname *buf);
其中uname(2)以buf指向的结构返回信息。您也可以从/usr/include/"$(arch)"-linux-gnu/sys/utsname.h读取头文件utsname.h进行更深入的研究。
看看man 2 uname以获得更多有关此的想法。
次佳办法
程序strace允许我们查看应用程序可能进行的系统调用。使用uname -a显然，只有open调用转到系统库，因此从技术上讲，文件系统上没有文件可供uname打开以进行读取。而是使用C库进行系统调用。
正如heemayl正确指出的那样，存在sys调用来检索存储在uname结构中的信息。这是手册页，建议以下内容：
This is a system call, and the operating system presumably knows its name, release and version . . . . . . Part of the utsname information is also accessible via /proc/sys/ker‐ nel/{ostype, hostname, osrelease, version, domainname}.
Part of the utsname information is also accessible via /proc/sys/ker‐ nel/{ostype, hostname, osrelease, version, domainname}.
但是，/proc文件系统是虚拟的，这意味着它仅在操作系统运行时存在。因此，在某种程度上，它是在内核或系统库中设置的。
最后，通读可以通过apt-get source coreutils获得的uname.c的源代码，我们可以看到它确实使用了utsname.h库(带有行号打印)：
19
20 #include <config.h>
21 #include <stdio.h>
22 #include <sys/types.h>
23 #include <sys/utsname.h>
24 #include <getopt.h>
25
strace输出：
skolodya@ubuntu:$ strace uname -a
execve("/bin/uname", ["uname", "-a"], [/* 58 vars */]) = 0
brk(0) = 0x1478000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7efee6935000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=137226, ...}) = 0
mmap(NULL, 137226, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7efee6913000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320\37\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1840928, ...}) = 0
mmap(NULL, 3949248, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7efee6350000
mprotect(0x7efee650b000, 2093056, PROT_NONE) = 0
mmap(0x7efee670a000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1ba000) = 0x7efee670a000
mmap(0x7efee6710000, 17088, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7efee6710000
close(3) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7efee6912000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7efee6910000
arch_prctl(ARCH_SET_FS, 0x7efee6910740) = 0
mprotect(0x7efee670a000, 16384, PROT_READ) = 0
mprotect(0x606000, 4096, PROT_READ) = 0
mprotect(0x7efee6937000, 4096, PROT_READ) = 0
munmap(0x7efee6913000, 137226) = 0
brk(0) = 0x1478000
brk(0x1499000) = 0x1499000
open("/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=7216688, ...}) = 0
mmap(NULL, 7216688, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7efee5c6e000
close(3) = 0
uname({sys="Linux", node="eagle", ...}) = 0
fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7efee6934000
uname({sys="Linux", node="eagle", ...}) = 0
uname({sys="Linux", node="eagle", ...}) = 0
write(1, "Linux eagle 4.1.0-040100rc2-gene"..., 113Linux eagle 4.1.0-040100rc2-generic #201505032335 SMP Mon May 4 03:36:35 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
) = 113
close(1) = 0
munmap(0x7efee6934000, 4096) = 0
close(2) = 0
exit_group(0) = ?
+++ exited with 0 +++
第三种办法
当然，heemayl的答案是正确的。
只是为了好玩，这是一个工作的C代码片段，展示了uname()(如果需要的话，这是一种自制的uname)返回的数据：使用gcc uname.c -o uname进行编译并使用./uname进行运行：
#include <stdio.h> // printf()
#include <sys/utsname.h> // uname()
int main() {
int ret; // stores the return value of uname()
struct utsname utsname; // stores the data returned by uname()
struct utsname *utsname_ptr = &utsname; // pointer to the struct holding the data returned by uname()
ret = uname(utsname_ptr); // calls uname() on utsname_ptr and stores its return value in ret
/* prints the fields of utsname */
printf("%s\n", utsname.sysname);
printf("%s\n", utsname.nodename);
printf("%s\n", utsname.release);
printf("%s\n", utsname.version);
printf("%s\n", utsname.machine);
/* returns the return value of uname() */
return(ret);
}
% ./uname
Linux
user-X550CL
4.2.0-25-generic
#30-Ubuntu SMP Mon Jan 18 12:31:50 UTC 2016
x86_64
第四种办法
除了heemayl的答案之外，您还可以从/proc/version获得一些信息，例如在uname命令中。