进程基本信息
环境变量: getenv与environ
下面代码列出了三种获取全部环境变量的方法:
#include <stdio.h>
#include <stdlib.h>
void t1() {
printf("LANG=%s\n", getenv("LANG"));
printf("PWD=%s\n", getenv("PWD"));
printf("SHELL=%s\n", getenv("SHELL"));
}
extern char** environ;
void t2() {
int i = 0;
while (environ[i] != NULL) printf("environ[%d]=%s\n", i, environ[i]), ++i;
}
/* environ[0]=SHELL=/bin/bash */
int main(int argc, char* argv[], char* envp[]) {
/* t1(); */
t2();
/* for (int i = 0; envp[i] != NULL; ++i) */
/* printf("envp[%d]=%s\n", i, envp[i]); */
return 0;
}
getenv函数, 需要制定参数, 给出值.environ全局变量, 直接遍历此二维字符数组指针, 即可得到信息.- 直接传入
main的第三个参数char* envp[], 与2一样, 遍历即可.
当然, 通过Shell程序printenv可以一次性获取全部键值对:
$ printenv | cat -n # 加上行号
1 SHELL=/bin/bash
2 NVM_INC=/home/zorch/.nvm/versions/node/v16.18.1/include/node
3 CONDA_EXE=/home/zorch/miniforge3/bin/conda
进程/(有效)用户/(有效)组ID
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char *argv[]) {
printf("pid=%d\n", getpid());
printf("ppid=%d\n", getppid());
printf("uid=%d\n", getuid());
printf("euid=%d\n", geteuid());
printf("gid=%d\n", getgid());
printf("egid=%d\n", getegid());
return 0;
}
/* pid=57663 */
/* ppid=57658 */
/* uid=1001 */
/* euid=1001 */
/* gid=1001 */
/* egid=1001 */
库/系统信息
glibc库版本
#include <stdio.h>
#include <stdlib.h>
#include <gnu/libc-version.h> // gnu_get_libc_version
int main(int argc, char *argv[]) {
printf("glibc version=%s\n", gnu_get_libc_version());
// clang
/* glibc version=2.31 */
// gcc
/* glibc version=2.35 */
printf("glibc version=%d.%d\n", __GLIBC__, __GLIBC_MINOR__);
return 0;
}
系统信息: uname
man 2 uname
#include <stdio.h>
#include <stdlib.h>
#include <sys/utsname.h>
int main(int argc, char *argv[]) {
struct utsname uts;
if (uname(&uts) == -1) fprintf(stderr, "uname"), exit(1);
printf("Node name: %s\n", uts.nodename);
printf("System name: %s\n", uts.sysname);
printf("Release: %s\n", uts.release);
printf("Version: %s\n", uts.version);
printf("Machine: %s\n", uts.machine);
#ifdef _GNU_SOURCE
printf("Domain name: %s\n", uts.domainname);
#endif
exit(EXIT_SUCCESS);
return 0;
}
/* Node name: xxx */
/* System name: Linux */
/* Release: 5.4.0-135-generic */
/* Version: #152-Ubuntu SMP Wed Nov 23 20:19:22 UTC 2022 */
/* Machine: x86_64 */
系统限制
运行时获取系统限制:
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
static void /* Print 'msg' plus sysconf() value for 'name' */
sysconfPrint(const char *msg, int name) {
long lim;
errno = 0;
lim = sysconf(name);
if (lim != -1) { /* Call succeeded, limit determinate */
printf("%s %ld\n", msg, lim);
} else {
if (errno == 0) /* Call succeeded, limit indeterminate */
printf("%s (indeterminate)\n", msg);
else /* Call failed */
/* errExit("sysconf %s", msg); */
fprintf(stderr, "error \n");
}
}
extern char *program_invocation_name;
extern char *program_invocation_short_name;
int main(int argc, char *argv[]) {
sysconfPrint("_SC_ARG_MAX: ", _SC_ARG_MAX);
sysconfPrint("_SC_LOGIN_NAME_MAX: ", _SC_LOGIN_NAME_MAX);
sysconfPrint("_SC_OPEN_MAX: ", _SC_OPEN_MAX);
sysconfPrint("_SC_NGROUPS_MAX: ", _SC_NGROUPS_MAX);
sysconfPrint("_SC_PAGESIZE: ", _SC_PAGESIZE);
sysconfPrint("_SC_RTSIG_MAX: ", _SC_RTSIG_MAX);
printf("absolute path=%s\n", program_invocation_name);
printf("relative path=%s\n", program_invocation_short_name);
exit(EXIT_SUCCESS);
}
/* _SC_ARG_MAX: 2097152 */
/* _SC_LOGIN_NAME_MAX: 256 */
/* _SC_OPEN_MAX: 65535 */
/* _SC_NGROUPS_MAX: 65536 */
/* _SC_PAGESIZE: 4096 */
/* _SC_RTSIG_MAX: 32 */
/* absolute path=./sysconf-1.out */
/* relative path=sysconf-1.out */
运行时获取与文件/路径相关的限制:
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
static void /* Print 'msg' plus value of fpathconf(fd, name) */
fpathconfPrint(const char *msg, int fd, int name) {
long lim;
errno = 0;
lim = fpathconf(fd, name);
if (lim != -1) { /* Call succeeded, limit determinate */
printf("%s %ld\n", msg, lim);
} else {
if (errno == 0) /* Call succeeded, limit indeterminate */
printf("%s (indeterminate)\n", msg);
else /* Call failed */
/* errExit("fpathconf %s", msg); */
fprintf(stderr, "error");
}
}
int main(int argc, char *argv[]) {
fpathconfPrint("_PC_NAME_MAX: ", STDIN_FILENO, _PC_NAME_MAX);
fpathconfPrint("_PC_PATH_MAX: ", STDIN_FILENO, _PC_PATH_MAX);
fpathconfPrint("_PC_PIPE_BUF: ", STDIN_FILENO, _PC_PIPE_BUF);
exit(EXIT_SUCCESS);
}
/* _PC_NAME_MAX: 255 */
/* _PC_PATH_MAX: 4096 */
/* _PC_PIPE_BUF: 4096 */