命令行和代码块之间的输出不同

我正在尝试实现一个库（在Linux上）来检查正在运行的程序的更多实例 .

程序获取正在运行的程序的可执行文件名，并将其与程序PID一起保存到二进制文件（ .existence ）中 .

在程序运行之前（再次），通过检查是否存在 .existence 文件来检查是否已存在该程序的实例，如果是，则进行比较 .

一切都在 codeblocks 中按预期工作，但是当我在命令行中运行时，返回程序PID的函数（ int find_pid ( const char *const instance ) ）返回 0 .

这是程序的一部分，可以编译和测试：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

void write_bin_file     ( const char *const fileName, const char *const msg );
char *read_bin_File     ( const char *const fileName );
char *my_strtok   ( char *msg );

int find_pid ( const char *const instance );

int main ( int argc, char *argv[] )
{
    char instance[ strlen( argv[0] ) + 1 ];
    memset( instance, '\0', sizeof( instance ) );

    if ( argc < 2 )
    {
        strcpy( instance, argv[0] );

        char *buffer = my_strtok( instance );

        write_bin_file ( ".existence", buffer );

        char *ret = read_bin_File( ".existence" );
        printf( "\n%s\n", ret );

        printf("Actc_pid =\t%d\n", getpid() );
        printf("Find_pid =\t%d\n", find_pid ( buffer ) );
        free( ret );
    }

    sleep( 5 );
}

char *read_bin_File ( const char *const fileName )
{
    FILE *fp = fopen( fileName, "rb" );
    if ( fp == NULL )
    {
        return NULL;
    }

    unsigned short len = 0;
    fread( &len, sizeof(unsigned short), 1, fp);

    char *buffer = malloc( sizeof( *buffer ) * len );
    fread( buffer, sizeof( *buffer ), len, fp );

    fclose(fp);
    return buffer;
}

void write_bin_file( const char *const fileName, const char *const msg )
{
    FILE *fp = fopen( fileName, "wb");
    if ( fp == NULL )
    {
        printf( "Error, write_bin_file()\n" );
        exit( EXIT_FAILURE );
    }
    size_t len = strlen( msg ) + 1;
    fwrite( &len, sizeof( unsigned short ), 1, fp);
    fwrite( msg, sizeof(char), len, fp);
    fclose( fp );
}

int find_pid ( const char *const instance )
{
    char line[256];
    memset( line, '\0', sizeof( *line ) );

    char buffer[555];
    memset( buffer, '\0', sizeof( *buffer ) );

    sprintf( buffer, "ps -A | grep %s", instance );
    FILE *cmd = popen( buffer, "r");

    fgets( line, 256, cmd);
    pid_t pid = (pid_t)strtoul(line, NULL, 10);

    pclose( cmd );
    return pid;
}

char *my_strtok( char *msg )
{
    char *ret = NULL;
    char *tmp = strtok( msg, "/" );
    while ( tmp != NULL )
    {
        ret = tmp;
        tmp = strtok( NULL, "/");
    }

    if ( ret == NULL )
    {
        return NULL;
    }

    return ret;
}

代码块输出：

program
Actc_pid =  11890
Find_pid =  11890

命令行输出：

program
Actc_pid =  11900
Find_pid =  0

Valgrind的：

valgrind --leak-check=full --track-origins=yes --show-leak-kinds=all Templates/Program/bin/Debug/Program
==12414== Memcheck, a memory error detector
==12414== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==12414== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==12414== Command: Templates/Program/bin/Debug/Program
==12414== 

Program
Actc_pid =  12414
Find_pid =  0
==12414== 
==12414== HEAP SUMMARY:
==12414==     in use at exit: 0 bytes in 0 blocks
==12414==   total heap usage: 8 allocs, 8 frees, 14,686 bytes allocated
==12414== 
==12414== All heap blocks were freed -- no leaks are possible
==12414== 
==12414== For counts of detected and suppressed errors, rerun with: -v
==12414== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)