Prova pratica 2014.09.25
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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')