uptime指令的简单实现

/* ** FILE: uptime.c ** NOTE: 2015-09-23 created by Jack Liu */ #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <utmp.h> #include "uptime.h" int get_uptime( double *dpUT ) { FILE *fp = NULL; double dIdleTime = 0; if( ( fp = fopen( UPTIME_FILE, "r" ) ) == NULL ) { fprintf( stderr, "fopen error\n" ); return -1; } if( fscanf( fp, "%lf %lf", dpUT, &dIdleTime ) != 2 ) { fprintf( stderr, "fscanf error\n" ); return -1; } fclose( fp ); return 0; } int get_avgload( double *dpOneAL, double *dpFivAL, double *dpFifAL ) { FILE *fp = NULL; if( ( fp = fopen( AVGLOAD_FILE, "r" ) ) == NULL ) { fprintf( stderr, "fopen error\n" ); return -1; } if( fscanf( fp, "%lf %lf %lf", dpOneAL, dpFivAL, dpFifAL ) != 3 ) { fprintf( stderr, "fscanf error\n" ); return -1; } fclose( fp ); return 0; } int get_userno( int *iUsers ) { int fd = -1; struct utmp stEntry; int iEntSize = sizeof( struct utmp ); int iRdNum = 0; *iUsers = 0; if( ( fd = open( UTMP_FILE, O_RDONLY ) ) < 0 ) { fprintf( stderr, "open error\n" ); return -1; } while( ( iRdNum = read( fd, &stEntry, iEntSize ) ) == iEntSize ) { if( stEntry.ut_type == USER_PROCESS ) ++( *iUsers ); } if( iRdNum < 0 ) { close( fd ); fprintf( stderr, "read error\n" ); return -1; } close( fd ); return 0; }