"Fourth edition of Linux Programming", chapter Fourth of the exercises

1, P128

A program that gets the date-time format to get the date of the time.

#include <stdio.h> #include <time.h>int main (int argc,char** argv) {struct tm* Time1,*time_trans;    Temporal data Structure time_t Alt;char c_time[128];char* result;char* result1= ""; Time (&alt); Time1=localtime (&alt)   ; Returns the local time stored in the data structure printf ("The date is%d.%d.%d \ n", time1->tm_year,time1->tm_mon,time1->tm_mday);   printf ("The date is%s \ n", CTime (&alt));    CTime convert the data structure into string return strftime (c_time,128, "%Y%B%d  %p%i:%m:%s", time1);    Format to save time to C_time string printf ("%s\n", C_time); strcpy (C_time, "Mar 2008,12:13:14");p rintf ("Now trans, the time%s \ n", c_ time); Result=strptime (C_time, "%d%b%y,%r:%s", Time_trans);p rintf ("%s \ n", result),//printf ("%d", strcmp (result1, "Ye ")" if (strcmp (RESULT,RESULT1) ==0) {printf ("%d%d%d\n", time_trans->tm_hour,time_trans->tm_min,time_trans- >TM_SEC);} return 0;}

2, P130, 132

A program that creates temporary files, obtains user information, and outputs logs.

#include <stdio.h> #include <pwd.h> #include <sys/types.h> #include <syslog.h>int main (int argc , char** argv) {uid_t id;struct passwd *pw; file* tempfile;char* filename;id=getuid ();     Gets the user's uidpw=getpwuid (ID); Get the PW file information for user uid printf ("UID PASSWORD entry:\n name=%s,uid=%d,home=%s,shell=%s\n", Pw->pw_name,pw->pw_uid, pw- >pw_dir,pw->pw_shell);p W=getpwnam ("root"); Get the PW file information for user root printf ("ROOT PASSWORD entry:\n name=%s,uid=%d,home=%s,shell=%s\n", Pw->pw_name,pw->pw_uid, Pw->pw_dir, Pw->pw_shell); while (Pw=getpwent ())//Get all user's pw file information {//printf ("UID PASSWORD entry:\n name=%s,uid= %d,home=%s,shell=%s\n ", Pw->pw_name,pw->pw_uid, Pw->pw_dir, Pw->pw_shell);} Filename=tmpnam ((void*) 0);         Returns a unique filename tempfile=fopen (filename, "R");      if (!tempfile) {syslog (log_err| Log_user, "oops-%m\n");} Tempfile=tmpfile ();            Returns a file with a unique file name File*if (!tempfile) {syslog (log_err| Log_user, "%m\n");} return 0;}

3, P141

A resource that restricts the CPU consumption of the program.

#include <stdio.h> #include <sys/time.h> #include <sys/types.h> #include <sys/resource.h># Include<math.h>void () {char* tmpstr= "What ' s wrong \ n"; file* f;//f=fopen ("haha", "w+"); F=tmpfile (); int i=0;if (!f) {printf ("?? \ n ");} for (; i<1000000;i++) {fwrite (tmpstr, sizeof (TMPSTR), 1,f), if (Ferror (f)) {fprintf (stderr, "wrong"); return;}} I=0;for (; i < 10000000; ++i) {int k;k= (1.1+i*i);} F.close ();} int main (int argc,char** argv) {struct rusage r_usage;struct rlimit r_limit;int pro;fun (); Getrusage (rusage_self,&r_ usage);   The information to get the program running is stored in the struct rusage printf ("CPU usage:user=%d.%0 6d,system==%d.%0 6d\n ", R_usage.ru_utime.tv_sec, r_usage.ru_utime.tv_usec,r_usage.ru_stime.tv_sec,r_usage.ru_stime.tv_sec);p ro= GetPriority (Prio_process,getpid ());  Get the priority of the program printf ("Current priority:%d\n", pro); R_limit.rlim_cur=2048;r_limit.rlim_max=4096;setrlimit (Rlimit_ Fsize,&r_limit);    Set some resource limits for the program Fun (); return 0;}

"Fourth edition of Linux Programming", chapter Fourth of the exercises