c - 如何从/proc/pid/打印信息

Question

今天的第二个问题，第一个问题确实有帮助。

这是我的代码:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/procfs.h>
#include <sys/fcntl.h>
#include <pwd.h>
char *getWaitChannel(int pid);
char *getPath(int pid);
char *getUserName(int uid);
int getBytes(int pid);
int main(int argc, char *argv[])
{
    long x;
    if (argc < 2){
    //error message
}
    x = strtol(argv[1], NULL, 10);
    printf("Good 1\n");
    get_info(x, argc, argv);
}
int get_info(pid_t pid)
{
    char path[40], line[100], *p, stateChar[100], Name[100];
    FILE* statusf;
    char buf[100];
    printf("This is pid %d\n", pid);
    int uid, vM;
    snprintf(path, 40, "/proc/%d/status", pid);
    statusf = fopen(path, "r");
    if(statusf == NULL)
        return -1;

    while(fgets(buf,sizeof buf, statusf) != NULL){

    sscanf(buf, "State:  %s", stateChar);
    sscanf(buf, "Name:  %s", Name);
    sscanf(buf, "Uid:     %d", &uid);
    sscanf(buf, "VmPeak: %d", &vM);

}
    char *channel = getWaitChannel(pid);
    char *full_path = getPath(pid);
    char *user = getUserName(uid);
    int b = getBytes(pid);
    printf("State: %s\n", stateChar);
    printf("Name: %s\n", Name);
    printf("Uid: %d\n", uid);
    printf("Username: %s\n", user);
    printf("Max Virtual Memory: %d\n", vM);
    printf("Full Path: %s\n", full_path);
    printf("Bytes written to storage layer: %d\n", b);
    printf("Waiting channel: %s\n", channel);

}
char *getUserName(int uid)
{
    struct passwd *pw = getpwuid(uid);
    if (pw)
    {
        return pw->pw_name;
    }
    return "";
}
int getBytes(int pid)
{   
    FILE* statusf2;
    char path[40];
    char buf2[100];
    int storage_bytes;
    snprintf(path, 40, "/proc/%d/io", pid);
    statusf2 = fopen(path, "r");
    if(statusf2 == NULL)
        return -1;

    while(fgets(buf2,sizeof buf2, statusf2) != NULL){
    sscanf(buf2, "write_bytes:  %d", &storage_bytes);
    return storage_bytes;
    }   
}
char *getPath(int pid)
{   
    FILE* statusf3;
    char path[40];
    char buf3[100];
    char *fullpath;
    snprintf(path, 40, "/proc/%d/cmdline", pid);
    statusf3 = fopen(path, "r");
    if(statusf3 == NULL)
        return "";

    while(fgets(buf3,sizeof buf3, statusf3) != NULL){
    sscanf(buf3,"/ %s", fullpath);
    return fullpath;
}
}
char *getWaitChannel(int pid)
{   
    FILE* statusf4;
    char path[40];
    char buf4[100];
    char *channel;
    snprintf(path, 40, "/proc/%d/stack", pid);
    statusf4 = fopen(path, "r");
    if(statusf4 == NULL)
        return "";

    while(fgets(buf4,sizeof buf4, statusf4) != NULL){
    sscanf(buf4,"[<c0227f4e>] %s", channel);
    return channel;
}
}

我正在获取有关名称、状态、UID 和用户名以及 VmPeak 的信息。他们正在按照我想要的方式工作。但其他 3 个是我似乎无法使它们工作的问题，我无法找出原因(完整路径、写入存储层的字节和等待 channel )。所以我的问题是如何访问它们并打印信息。

Answer 1

如 alk 所示，修改 getWaitChannel() 为 channel 分配内存。稍后不需要 channel 数据时需要释放内存。

char *getWaitChannel(int pid)
{
    FILE* statusf4;
    char path[40];
    char buf4[100];
    char *channel;
    channel = malloc(1024);
    /* Add error handling for malloc failure here */

    snprintf(path, 40, "/proc/%d/stack", pid);
    statusf4 = fopen(path, "r");
    if(statusf4 == NULL)
        return "";

    while(fgets(buf4,sizeof buf4, statusf4) != NULL){
    sscanf(buf4,"[<c0227f4e>] %s", channel);
    return channel;
}
}

检查您的代码，看看是否有任何其他变量(例如完整路径)需要内存分配，并通过注释代码的某些部分来捕获错误来执行逐步调试。