C fscanf дает мне повторяющиеся строки

Я пытаюсь отобразить детали каждого процесса, перенаправляя вывод команды «ps». Я перенаправил вывод ps в файл. Я читаю из него и отображаю PID и команду с помощью fscanf. Но я вижу, что некоторые строки дублируются, а в некоторых случаях отрицательное значение для Pids.

void TR69_DM_GetProcDetails(char *FileName, int32_t *ProcCount, struct ProcessInfo *ProcVar)
{
    char CharBuf[BUF_SIZE] ;
    int32_t i = 0;

    int Pid;
    char Cmd[100];

    FILE *FileDesc;
    FileDesc = fopen (FileName, "r");

    printf("\nFile pointer %ld\n", ftell(FileDesc));
    fscanf (FileDesc, "%[^\n]\n", CharBuf);
    puts(CharBuf);

    printf("\nFile pointer %ld\n", ftell(FileDesc));

    while ( EOF != fscanf (FileDesc, "%*s %lu %*d %*d %*s %*s %*s %s", &Pid, Cmd))
    {
        printf("\n PID is %d and cmd is %s", Pid, Cmd);
    //  i++;
    }

}

и я получаю следующий образец вывода:

 PID is 2104 and cmd is /usr/lib/indicator-datetime/indicator-datetime-service
 PID is 2107 and cmd is /usr/lib/indicator-messages/indicator-messages-service
 PID is 2114 and cmd is /usr/lib/indicator-session/indicator-session-service
 PID is 2134 and cmd is /usr/lib/geoclue/geoclue-master
 PID is 2142 and cmd is gnome-screensaver
 PID is 2145 and cmd is /usr/lib/gnome-disk-utility/gdu-notification-daemon
 PID is 2342 and cmd is /usr/bin/python
 PID is 2342 and cmd is /usr/bin/python
 PID is 4316 and cmd is /sbin/dhclient
 PID is -4 and cmd is /sbin/dhclient
 PID is -4 and cmd is /sbin/dhclient
 PID is -4 and cmd is /sbin/dhclient
 PID is -4 and cmd is /sbin/dhclient
 PID is -4 and cmd is /sbin/dhclient
 PID is -4 and cmd is /sbin/dhclient
 PID is -4 and cmd is /sbin/dhclient
 PID is -4 and cmd is /sbin/dhclient
 PID is -4 and cmd is /sbin/dhclient
 PID is -4 and cmd is /sbin/dhclient
 PID is 4444 and cmd is /usr/sbin/ntpd
 PID is 4444 and cmd is /usr/sbin/ntpd
 PID is 4444 and cmd is /usr/sbin/ntpd
 PID is 4444 and cmd is /usr/sbin/ntpd
 PID is 113 and cmd is /usr/sbin/ntpd
 PID is 113 and cmd is /usr/sbin/ntpd
 PID is 5411 and cmd is sshd:
 PID is 5411 and cmd is sshd:
 PID is 5411 and cmd is sshd:
 PID is 5584 and cmd is sshd:
 PID is 5584 and cmd is sshd:
 PID is 5585 and cmd is -bash
 PID is 6790 and cmd is /usr/lib/firefox-4.0.1/firefox-bin
 PID is 7007 and cmd is /usr/lib/firefox-4.0.1/plugin-container
 PID is 7007 and cmd is /usr/lib/firefox-4.0.1/plugin-container
 PID is 7007 and cmd is /usr/lib/firefox-4.0.1/plugin-container
 PID is 6790 and cmd is /usr/lib/firefox-4.0.1/plugin-container
 PID is 6790 and cmd is /usr/lib/firefox-4.0.1/plugin-container
 PID is 6790 and cmd is /usr/lib/firefox-4.0.1/plugin-container
 PID is 7023 and cmd is /usr/lib/nspluginwrapper/i386/linux/npviewer.bin
 PID is 7023 and cmd is /usr/lib/nspluginwrapper/i386/linux/npviewer.bin
 PID is 7023 and cmd is /usr/lib/nspluginwrapper/i386/linux/npviewer.bin
 PID is 7023 and cmd is /usr/lib/nspluginwrapper/i386/linux/npviewer.bin
 PID is 7023 and cmd is /usr/lib/nspluginwrapper/i386/linux/npviewer.bin
 PID is 8390 and cmd is man
 PID is 8390 and cmd is man
 PID is 8402 and cmd is pager
 PID is 8402 and cmd is pager
 PID is 8827 and cmd is ping
 PID is 8827 and cmd is ping
 PID is 8869 and cmd is bash
 PID is 8907 and cmd is bash
 PID is 12637 and cmd is cat
 PID is 12637 and cmd is cat
 PID is 15164 and cmd is tftp
 PID is 15185 and cmd is vim
 PID is 15185 and cmd is vim
 PID is 16827 and cmd is telnet
 PID is 16827 and cmd is telnet
 PID is 17117 and cmd is sshd:
 PID is 17117 and cmd is sshd:
 PID is 17117 and cmd is sshd:
 PID is 17226 and cmd is sshd:
 PID is 17226 and cmd is sshd:
 PID is 17227 and cmd is -sh
 PID is 18120 and cmd is su
 PID is 18127 and cmd is bash
 PID is 18896 and cmd is sshd:
 PID is 18896 and cmd is sshd:
 PID is 18896 and cmd is sshd:
 PID is 19069 and cmd is sshd:
 PID is 19069 and cmd is sshd:
 PID is 19070 and cmd is -sh
 PID is 20313 and cmd is gedit
 PID is 20313 and cmd is gedit
 PID is 20313 and cmd is gedit
 PID is 20334 and cmd is ssh
 PID is 20334 and cmd is ssh
 PID is 20337 and cmd is [kworker/1:1]
 PID is 20341 and cmd is su
 PID is 20349 and cmd is bash
 PID is 20371 and cmd is [kworker/0:1]
 PID is 20375 and cmd is [kworker/0:2]
 PID is 20377 and cmd is [kworker/1:0]
 PID is 21342 and cmd is [kjournald]
 PID is 23384 and cmd is /opt/Adobe/Reader9/Reader/intellinux/bin/acroread
 PID is 23384 and cmd is /opt/Adobe/Reader9/Reader/intellinux/bin/acroread
 PID is 23495 and cmd is gnome-terminal
 PID is 23498 and cmd is gnome-pty-helper
 PID is 23499 and cmd is bash
 PID is 26446 and cmd is ssh
 PID is 26446 and cmd is ssh
 PID is 26733 and cmd is sshd:
 PID is 26733 and cmd is sshd:
 PID is 26843 and cmd is -bash
 PID is 26943 and cmd is sshd:
 PID is 26943 and cmd is sshd:
 PID is 27036 and cmd is sshd:
 PID is 27036 and cmd is sshd:
 PID is 27036 and cmd is sshd:
 PID is 27052 and cmd is /usr/lib/openssh/sftp-server
 PID is 27149 and cmd is sshd:
 PID is 27149 and cmd is sshd:
 PID is 27150 and cmd is -bash
 PID is 27734 and cmd is ssh
 PID is 27734 and cmd is ssh
 PID is 28265 and cmd is bin/TR69_DM
 PID is 0 and cmd is bin/TR69_DM
 PID is 28266 and cmd is ps
 PID is 28266 and cmd is ps
 PID is 29510 and cmd is su
 PID is 29510 and cmd is su
 PID is 29517 and cmd is bash
 PID is 29951 and cmd is minicom
 PID is 30056 and cmd is bash
 PID is 30293 and cmd is bash
 PID is 30329 and cmd is ssh
 PID is 30329 and cmd is ssh
 PID is 30597 and cmd is bash
 PID is 30632 and cmd is ssh
 PID is 30632 and cmd is ssh
 PID is 31508 and cmd is bash

Что могло пойти не так?


c linux scanf pid ps
person Christy George    schedule 21.02.2014    source источник
comment
не могли бы вы сказать нам, в каком формате данные содержатся в файле.   -  person ajay    schedule 21.02.2014
comment
@Ajay, файл содержит перенаправленный вывод команды linux ps -ef   -  person Christy George    schedule 24.02.2014

Ответы (1)


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fscanf() возвращает количество выполненных назначений. Проверка на EOF недостаточна, так как некоторые назначения могли быть выполнены, а остальные нет, что означает, что последующий код будет обрабатывать устаревшие или неинициализированные значения. Следующий цикл остановит обработку на первой строке, если формат окажется непредвиденным, и избежит устаревших значений:

while ( 2 == fscanf (FileDesc, "%*s %lu %*d %*d %*s %*s %*s %s", &Pid, Cmd))
{
}

Улучшенное решение будет использовать fgets() для чтения строки, а затем использовать sscanf() для анализа прочитанной строки. Это позволит вам обнаружить EOF и разрешить несколько попыток анализа строки с использованием разных форматов:

char line[1024];
while (fgets(line, sizeof(line), stdin))
{
    if (2 == sscanf (line, "%*s %lu %*d %*d %*s %*s %*s %s", &Pid, Cmd))
    {
    }
    else if (2 == sscanf (line, "some-other-format", &Pid, Cmd))
    {
    }
    else
    {
        fprintf(stderr, "Unable to parse '%s'\n", line);
    }
}

Кроме того, предотвратите потенциальное переполнение буфера, указав максимальное количество символов, которое sscanf() должен записать в Cmd. Это должно быть на единицу меньше размера Cmd, оставляя место для завершающего нулевого символа. Например:

if (2 == sscanf(line, "%lu %255s", &Pid, Cmd))
person hmjd    schedule 21.02.2014
comment
Полностью собираюсь проголосовать за это, но я думаю, вы хотели использовать sscanf и line во втором фрагменте. (если я правильно следовал вашей логике, которая у меня всегда ерунда). - person WhozCraig; 21.02.2014
comment
@WhozCraig, спасибо, именно это я и имел в виду. Отредактировано. - person hmjd; 21.02.2014
comment
Безопасное и правильное использование scanf нетривиально. Хороший ответ. - person ajay; 21.02.2014