linux - [Solved-5 Solutions] Linux API to list running processes ? - ubuntu - red hat - debian - linux server - linux pc

Linux API to list running processes ?

You can use proc

/procps-3.2.8/proc/readproc.c

API provided by libproc, which should be available in your repo but you will need the "-dev" variation for the headers.

You can consider writing a Kernel module which will implement your own system call. And your system call should be written so that it can obtain the list of current processes, such as:

/* ProcessList.c 
    Robert Love Chapter 3
    */
    #include < linux/kernel.h >
    #include < linux/sched.h >
    #include < linux/module.h >

    int init_module(void)
    {
    struct task_struct *task;
    for_each_process(task)
    {
    printk("%s [%d]\n",task->comm , task->pid);
    }

    return 0;
    }

    void cleanup_module(void)
    {
    printk(KERN_INFO "Cleaning Up.\n");
    }

Here are some examples of program doing this:

But unfortunately, that does not constitute an API.

You can use (C/C++):

Ref Here: http://ubuntuforums.org/showthread.php?t=657097

#ifndef __cplusplus
    #define _GNU_SOURCE
#endif

#include <unistd.h>
#include <dirent.h>
#include <sys/types.h> // for opendir(), readdir(), closedir()
#include <sys/stat.h> // for stat()

#ifdef __cplusplus
    #include <iostream>
    #include <cstdlib>
    #include <cstring>
    #include <cstdarg>
#else
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <stdarg.h>
#endif


#define PROC_DIRECTORY "/proc/"
#define CASE_SENSITIVE    1
#define CASE_INSENSITIVE  0
#define EXACT_MATCH       1
#define INEXACT_MATCH     0


int IsNumeric(const char* ccharptr_CharacterList)
{
    for ( ; *ccharptr_CharacterList; ccharptr_CharacterList++)
        if (*ccharptr_CharacterList < '0' || *ccharptr_CharacterList > '9')
            return 0; // false
    return 1; // true
}


int strcmp_Wrapper(const char *s1, const char *s2, int intCaseSensitive)
{
    if (intCaseSensitive)
        return !strcmp(s1, s2);
    else
        return !strcasecmp(s1, s2);
}

int strstr_Wrapper(const char* haystack, const char* needle, int intCaseSensitive)
{
    if (intCaseSensitive)
        return (int) strstr(haystack, needle);
    else
        return (int) strcasestr(haystack, needle);
}


#ifdef __cplusplus
pid_t GetPIDbyName(const char* cchrptr_ProcessName, int intCaseSensitiveness, int intExactMatch)
#else
pid_t GetPIDbyName_implements(const char* cchrptr_ProcessName, int intCaseSensitiveness, int intExactMatch)
#endif
{
    char chrarry_CommandLinePath[100]  ;
    char chrarry_NameOfProcess[300]  ;
    char* chrptr_StringToCompare = NULL ;
    pid_t pid_ProcessIdentifier = (pid_t) -1 ;
    struct dirent* de_DirEntity = NULL ;
    DIR* dir_proc = NULL ;

    int (*CompareFunction) (const char*, const char*, int) ;

    if (intExactMatch)
        CompareFunction = &strcmp_Wrapper;
    else
        CompareFunction = &strstr_Wrapper;


    dir_proc = opendir(PROC_DIRECTORY) ;
    if (dir_proc == NULL)
    {
        perror("Couldn't open the " PROC_DIRECTORY " directory") ;
        return (pid_t) -2 ;
    }

    // Loop while not NULL
    while ( (de_DirEntity = readdir(dir_proc)) )
    {
        if (de_DirEntity->d_type == DT_DIR)
        {
            if (IsNumeric(de_DirEntity->d_name))
            {
                strcpy(chrarry_CommandLinePath, PROC_DIRECTORY) ;
                strcat(chrarry_CommandLinePath, de_DirEntity->d_name) ;
                strcat(chrarry_CommandLinePath, "/cmdline") ;
                FILE* fd_CmdLineFile = fopen (chrarry_CommandLinePath, "rt") ;  // open the file for reading text
                if (fd_CmdLineFile)
                {
                    fscanf(fd_CmdLineFile, "%s", chrarry_NameOfProcess) ; // read from /proc/<NR>/cmdline
                    fclose(fd_CmdLineFile);  // close the file prior to exiting the routine

                    if (strrchr(chrarry_NameOfProcess, '/'))
                        chrptr_StringToCompare = strrchr(chrarry_NameOfProcess, '/') +1 ;
                    else
                        chrptr_StringToCompare = chrarry_NameOfProcess ;

                    //printf("Process name: %s\n", chrarry_NameOfProcess);
                    //printf("Pure Process name: %s\n", chrptr_StringToCompare );

                    if ( CompareFunction(chrptr_StringToCompare, cchrptr_ProcessName, intCaseSensitiveness) )
                    {
                        pid_ProcessIdentifier = (pid_t) atoi(de_DirEntity->d_name) ;
                        closedir(dir_proc) ;
                        return pid_ProcessIdentifier ;
                    }
                }
            }
        }
    }
    closedir(dir_proc) ;
    return pid_ProcessIdentifier ;
}

#ifdef __cplusplus
    pid_t GetPIDbyName(const char* cchrptr_ProcessName)
    {
        return GetPIDbyName(cchrptr_ProcessName, CASE_INSENSITIVE, EXACT_MATCH) ;
    }
#else
    // C cannot overload functions - fixed
    pid_t GetPIDbyName_Wrapper(const char* cchrptr_ProcessName, ... )
    {
        int intTempArgument ;
        int intInputArguments[2] ;
        // intInputArguments[0] = 0 ;
        // intInputArguments[1] = 0 ;
        memset(intInputArguments, 0, sizeof(intInputArguments) ) ;
        int intInputIndex ;
        va_list argptr;

        va_start( argptr, cchrptr_ProcessName );
            for (intInputIndex = 0;  (intTempArgument = va_arg( argptr, int )) != 15; ++intInputIndex)
            {
                intInputArguments[intInputIndex] = intTempArgument ;
            }
        va_end( argptr );
        return GetPIDbyName_implements(cchrptr_ProcessName, intInputArguments[0], intInputArguments[1]);
    }

    #define GetPIDbyName(ProcessName,...) GetPIDbyName_Wrapper(ProcessName, ##__VA_ARGS__, (int) 15)

#endif

int main()
{
    pid_t pid = GetPIDbyName("bash") ; // If -1 = not found, if -2 = proc fs access error
    printf("PID %d\n", pid);
    return EXIT_SUCCESS ;
}

• /proc is a special filesystem created on the fly by the kernel so that user mode processes can read data that will otherwise only be available for the kernel.
• The recommended way is therefore, reading from /proc.
• You can quickly look at the /proc filesystem to see how its structured. For every process there is a /proc/pid where pid is the process id number. Inside this folder there are several files which include different data about the current process.

If you run

strace ps -aux