Prova pratica 2014.09.25

Testo: [1]

Esercizio 1

Scrivere un programma che preso come parametro un file contenente un elenco di comandi (con I relativi parametri)
 li attivi tutti in esecuzione concorrente e rimanga in attesa. Quando il primo termina, vengono terminati (con segnale SIGTERM) tutti gli altri. 
(consiglio: puo' essere utile usare la mia libreria s2argv-execs)
esempio:
wta commands
il file commands contiene:
      ./ttest 40
      ./ttest 10
      ./ttest 20
lo script ./ttest contiene:
      #!/bin/bash
      echo waiting for $1 seconds
      sleep $1
      echo done $i
l'ouptut sara':
      waiting for 40 seconds
      waiting for 10 seconds
      waiting for 20 seconds
      done 10
e poi basta perche' gli altri processi verranno terminati.

Soluzione di Stefano Zaniboni

#include <stdio.h>
#include <s2argv.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <error.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <poll.h>

int main(int argc, char *argv[]){
   FILE *stream;
   char *line=NULL;
   size_t len=0;
   ssize_t read;
   int i=0;
   int status;
   pid_t fineFirst; /*memorizzo il pid del primo processo terminato*/
   pid_t all[i];
   int pipefd[2];
   struct pollfd pipe_read_poll;

   if(argc!=2){
      fprintf(stderr,"Argomento Mancante!\n");
      exit(1);
   }

   stream=fopen(argv[1], "r");
   if(stream == NULL)
      exit(EXIT_FAILURE);

   /*aprire una pipe, dentro al while dove ho la fork fare poll che aspetta un carattere dalla pipe. Lo mando finito il while*/
   pipe(pipefd);
   pipe_read_poll.fd = pipefd[0];
   pipe_read_poll.events = POLLIN;

   while((read = getline(&line, &len, stream)) != -1) {
      if(fork()==0){
         i++;
         char **lines=s2argv(line, NULL);
         poll(&pipe_read_poll,1,-1);
         execvp(lines[0], lines);
         all[i]=getpid(); /**/
         s2argv_free(lines);
         perror("execvp fail!");
         exit(1);
      }
      else
         exit(2);
   }

   /*inviare carattere alla pipe*/
   char buf='g';
   write(pipefd[1], &buf, 1);
   fineFirst=wait(&status);
   /*kill the rest of process*/
   while(i > 0){
      if(all[i] != fineFirst){
         kill(all[i], SIGTERM);
      }
      --i;
   }
   fclose(stream);
   exit(0);
}

Esercizio 2

Soluzione di LeonardoF

//ESERCIZIO 2
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "execs.h"  //https://github.com/rd235/s2argv-execs
#include <fcntl.h>

#define AOI_LENSTEP 8
#define BUFFLEN  256


struct array_of_integers {
    int **integers;
    size_t currentlength; //the length of number of integers in memory
    size_t arraylength; //the length of memory allocated
};
 
typedef struct array_of_integers array_of_integers;
 
void array_of_integers_add(array_of_integers *arrayOfIntegers, int val) {
   
    if (arrayOfIntegers->currentlength >= arrayOfIntegers->arraylength) {
        size_t newlength = arrayOfIntegers->arraylength + AOI_LENSTEP;
         int **new_vec = realloc(arrayOfIntegers->integers, newlength * sizeof(arrayOfIntegers->integers[0]));

        if (new_vec != NULL) {
            arrayOfIntegers->arraylength = newlength;
            arrayOfIntegers->integers = new_vec;
        }
    }
    if (arrayOfIntegers->currentlength < arrayOfIntegers->arraylength)  
        arrayOfIntegers->integers[arrayOfIntegers->currentlength] = malloc(sizeof(int));
        *(arrayOfIntegers->integers[arrayOfIntegers->currentlength++]) = val;


}
 
void array_of_integers_print(array_of_integers *v) {
    size_t i;
    for (i = 0; i < v->currentlength; i++)
        printf("[%3lu]: %d\n", i, *(v->integers[i]));
}


int main(int argc, char *argv[]) {
	/*opening and reading the file*/
    char* line = NULL;
    size_t lineLength = 0;
	ssize_t numberOfCharactersRead;
  

    FILE* fd1 = fopen(argv[1],"r");

    static array_of_integers arrayOfPid;
    static array_of_integers arrayOfFd;
    int fd; //file descriptor
    int i = 0; //iterator
    char concat[BUFFLEN];

    while ((numberOfCharactersRead = getline(&line, &lineLength, fd1)) >= 0) {
        if (line[numberOfCharactersRead - 1] == '\n')
            line[numberOfCharactersRead - 1] = 0;
       
 	///
 	/*done*/
 	/* opening output files, forking , saving pids and file descriptors*/
    sprintf(concat,"./temp%d",i);
    fd = open(concat,O_RDWR | O_CREAT | O_TRUNC , 0666);

 	int pid = fork();
 	switch(pid){
 		case 0: //children
                        //children stdio = file fd
                        dup2(fd,STDOUT_FILENO);
			//execution of the command
			execsp(line);
 		        exit(-1); // in case of execsp failure
 		default: //parent 
                         //must save all the pids
                         array_of_integers_add(&arrayOfPid,pid);
                         //must save all the fds. ( they will have the same order of the pids);
                         array_of_integers_add(&arrayOfFd,fd); 
 			
                         i ++;
 			 break;
 			}
 		
 	}
    free(line);
    /*done*/
    
    /*waiting first process and killing the others*/
    int firstpid;
    size_t j; //iterator
    size_t firstpid_pos; //position of the first pid in the array
    //wait the first process
    firstpid = wait(NULL);
 
    /*sigterm the other processes iterating the pids vector*/
    for (j = 0; j < (&arrayOfPid)->currentlength; j++){
        int temp = *((&arrayOfPid)->integers[j]);

        if(temp != firstpid)
            kill( temp,SIGTERM);
        else 
        	firstpid_pos = j ;
    }
    /*done*/

    /*printing the file of the "fisrt pid" process , unlinking the file and closing them*/
    for (j = 0; j < (&arrayOfFd)->currentlength; j++){
    	 fd = *((&arrayOfFd)->integers[j]);
    
    	sprintf(concat,"./temp%lu",j);

    	if (j == firstpid_pos){
    		int c;
    		//lseek is needed because the file is inherited
    		lseek(fd,0,SEEK_SET);
    		
    		FILE *fdp = fdopen(fd,"r");
    		while ((c = getc(fdp)) != EOF)
        		putchar(c);
    	}   	
    	//unlink file fd
    	unlink(concat);
    	//close file fd
    	close(fd);
    }
    /*done*/
    return 0;
}

--LeonardoF (talk) 11:33, 26 April 2017 (CEST)LeonardoF

Soluzione di Maldus

#include <s2argv.h>
#include <poll.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <signal.h>

int main(int argc, char* argv[]){
        int i=0, status, out;
        FILE *fd, *output;
        pid_t *idents, winner;
        char *line=NULL, *string;
        size_t n=1;
        int pipefd[2];
        pipe(pipefd);
        struct pollfd pipepoll;
        pipepoll.fd = pipefd[0];
        pipepoll.events = POLLIN;
        if( !(fd = fopen(argv[1], "r"))){
                perror("fopen:");
                exit(1);
        }
        while( getline(&line, &n, fd) > 0){
                i++;
                free(line);
                line=NULL;
        }
        idents = malloc(sizeof(pid_t)*i);
        rewind(fd);
        i = 0;
        while( getline(&line, &n, fd) >0 ){
                switch( idents[i]=fork()){
                        case 0:
                                asprintf( &string, "out%i" ,getpid());
                                if( (out=open(string, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR)) <0){
                                        perror("open");
                                        exit(1);
                                }
                                free(string);
                                dup2(out, 1);
                                close(out);
                                poll(&pipepoll, 1, -1);
                                execsp(line);
                                exit(0);
                        default:
                                free(line);
                                line=NULL;
                                i++;
                                break;
                }
        }
        write(pipefd[1], "g", 1);
        winner = wait(&status);
        i--;
        for( ; i >= 0 ; i--){
                if(idents[i]!=winner){
                        kill(idents[i], SIGTERM);
                        asprintf( &string, "out%i", idents[i]);
                        unlink(string);
                        free(string);
                }
        }
        asprintf( &string, "out%i" , winner);
        if( !(output = fopen(string, "r"))){
                perror("fopen");
                exit(1);
        }
        while( getline(&line, &n, output)>0){
                printf("%s", line);
                free(line);
                line=NULL;
        }
        unlink(string);
        fclose(fd);
        fclose(output);
        return 0 ;
}

Per stampare solo l'output del processo vincente salvo quello di ciascun processo in un file di testo ( che poi cancello ). Mi viene però da pensare che debba esistere un modo migliore per farlo...

Esercizio 3

Scrivere un programma python o uno scrip bash che faccia un backup storico di un file.
backn file n
deve mantenere n versioni del file specificato. n>2
Esempio:
backn miofile 10
se esiste miofile.9 deve essere rinominato in miofile.10
se esiste miofile 8 deve essere rinominato in miofile 9
e cosi' via fino a miofile.2, rinominato miofile 3.
ora se miofile.1 ha lo stesso contenuto di miofile.3, miofile diventa un link fisico a miofile.2
miofile viene copiato in miofile.1

Soluzione di Blissett

#! /bin/bash

if [[ $# != 2 || ! -f $1 ]]
then 
		echo "Usage: $0 file n_backup"
		exit -48
fi

file=$1
n_backup=$2
cartella="cartellaBackup"
true=0 

if [[ ! -d $cartella ]]
then
	mkdir $cartella
fi
cd ./$cartella

for i in `find ./ -name "$file*" | sort -n -r -t. -k3 | cut -d. -f3` 
do
	true=1
	tmp=`find ./ -name "$file.$i"`
	num=$(($i+1))
	mv $tmp "$file.$num"
	if [[ $num -gt n_backup ]]
	then
		rm "$file.$num"
	fi
done

if [[ $true -eq 1 ]]
then
	cmp -s "$file.2" "../$file"
	if [[ $? -eq 0 ]]
	then	
	echo creo link fisico.
		ln "$file.2" "$file.1"
	else
		cp ../$file ./
		mv $file "$file.1"
	fi
else
		cp ../$file ./
		mv $file "$file.1"
fi

--Blissett (talk) 13:14, 11 May 2015 (CEST)

Soluzione di Maldus

import argparse
import sys
import os
import shutil
import filecmp

def olderVersion( new, old ):
    new = new + '.'
    l = len(new)
    if new in old:
        try:
            num=int(old[l:])
            if num < args.version and num!=1 : os.rename(old, old[:l]+str(num+1))
        except ValueError:
            return 


parser = argparse.ArgumentParser(description='backup storico')
parser.add_argument('file', metavar='file', type=str, help='file di cui fare backup')
parser.add_argument('version', metavar='versione', type=int, help='numero di versione')
args = parser.parse_args()
new = args.file 

if args.version < 2:
    print("la versione deve essere > 2")
    sys.exit(1)

entries = [ x for x in os.listdir('.') if os.path.isfile(x)]
if not new in entries:
    print("Nessun file con quel nome")
    sys.exit(1)

for file in entries: olderVersion( new, file )

if new+'.2' in entries:
    if filecmp.cmp(new+'.3', new+'.1'): os.link(new, new+'.2')
    else: os.rename(new+'.1', new+'.2')
elif new+'.1' in entries: os.rename(new+'.1', new+'.2')

shutil.copyfile(new, new+'.1')