本文介绍了对于下面的C程序，execl的返回-1，标志着一个权限被拒绝的错误的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
对于下面的C程序，execl的返回-1，标志着一个权限被拒绝的错误。我查了读，写。执行我的可执行文件的权限和他们都RWX。可能有人请让我知道为什么execl的返回一个权限被拒绝的错误？非常感谢你。
的#include＆LT;＆stdio.h中GT;
＃包括LT＆;＆STDDEF.H GT;
＃包括LT＆;＆stdlib.h中GT;
＃包括LT＆;＆unistd.h中GT;
＃包括LT＆; SYS / types.h中＆GT;
＃包括LT＆; SYS / wait.h＆GT;
＃包括LT＆; SYS / stat.h＆GT;
＃包括LT＆;＆fcntl.h GT;
＃包括LT＆; SYS / shm.h＆GT;
＃包括LT＆;＆errno.h中GT;
＃包括LT＆;＆semaphore.h GT;＃定义MAXLINE 256
＃定义MAXARGS 128
＃定义SHELL/ H / fchang03/// bin / sh的的key_t shmkey;
INT的shmid;
sem_t * sem的;
INT * P;结构statStuff {
INT PID; //％d个
焦炭通讯[256]; //％S
焦状态; // ％C
INT PPID; //％d个
INT PGRP; //％d个
INT会议; //％d个
INT tty_nr; //％d个
INT tpgid; //％d个
无符号长标志; //％禄
无符号长minflt; //％禄
无符号长cminflt; //％禄
无符号长majflt; //％禄
无符号长cmajflt; //％禄
无符号长UTIME; //％禄
无符号长STIME; //％禄
长cutime; //％LD
长cstime; //％LD
长期优先; //％LD
长美观大方; //％LD
长NUM_THREADS; //％LD
长itrealvalue; //％LD
无符号长开始时间; //％禄
无符号长VSIZE; //％禄
长RSS; //％LD
无符号长RLIM; //％禄
无符号长启动code; //％禄
无符号长端code; //％禄
无符号长startstack; //％禄
无符号长kstkesp; //％禄
无符号长kstkeip; //％禄
无符号长信号; //％禄
无符号长堵塞; //％禄
无符号长sigignore; //％禄
无符号长sigcatch; //％禄
无符号长WCHAN; //％禄
无符号长nswap; //％禄
无符号长cnswap; //％禄
INT exit_signal; //％d个
INT处理器; //％d个
无符号长rt_priority; //％禄
unsigned long类型的政策; //％禄
无符号长长delayacct_blkio_ticks; //％LLU
};静态INT readStat（INT PID，结构statStuff * S）{ 为const char *格式=％d个％S％C％D％D％D％禄％禄％禄％禄％禄％禄％禄％LD％LD％LD％LD％LD％LD％禄％lu个％ld的％lu个％lu个％lu个％lu个％lu个％lu个％lu个％lu个％lu个％lu个％lu个％lu个％lu个％D％禄禄％LLU％; 焦炭BUF [256];
FILE * PROC;
sprintf的（BUF的/ proc /％D / STAT，PID）;
PROC = FOPEN（BUF，R）;
如果（PROC）{
如果（42 ==的fscanf（PROC，格式
＆安培; S-＆GT; PID，
S-GT＆;通讯，
＆安培; S-＆GT;的状态，
＆安培; S-＆GT; PPID，
＆安培; S-＆GT; PGRP，
＆安培; S-＆GT;会议，
＆安培; S-＆GT; tty_nr，
＆安培; S-＆GT; tpgid，
＆安培; S-＆GT;的标志，
＆安培; S-＆GT; minflt，
＆安培; S-＆GT; cminflt，
＆安培; S-＆GT; majflt，
＆安培; S-＆GT; cmajflt，
＆安培; S-＆GT; UTIME，
＆安培; S-＆GT; STIME，
＆安培; S-＆GT; cutime，
＆安培; S-＆GT; cstime，
＆安培; S-＆GT;的优先级，
＆安培; S-＆GT;不错，
＆安培; S-＆GT; NUM_THREADS，
＆安培; S-＆GT; itrealvalue，
＆安培; S-＆GT;开始时间，
＆安培; S-＆GT; VSIZE，
＆安培; S-＆GT; RSS，
＆安培; S-＆GT; RLIM，
＆安培; S-＆GT;启动code，
＆安培; S-＆GT;结束code，
＆安培; S-＆GT; startstack，
＆安培; S-＆GT; kstkesp，
＆安培; S-＆GT; kstkeip，
＆放大器; S-＆gt;信号，
＆安培; S-＆GT;受阻，
＆安培; S-＆GT; sigignore，
＆安培; S-＆GT; sigcatch，
＆安培; S-＆GT; WCHAN，
＆安培; S-＆GT; nswap，
＆安培; S-＆GT; cnswap，
＆安培; S-＆GT; exit_signal，
＆安培; S-＆GT;处理器，
＆安培; S-＆GT; rt_priority，
＆安培; S-＆GT;的政策，
＆安培; S-＆GT; delayacct_blkio_ticks
））{
的printf（堆栈开始=％X \\ n，S＆GT; startstack）;
的printf（堆栈结束=％X \\ n，S＆GT; kstkesp）;
FCLOSE（PROC）;
返回1;
}其他{
FCLOSE（PROC）;
返回0;
}
}其他{
返回0;
}
}INT的eval（为const char * CMDLINE）
{
的char * ARGV [MAXARGS]
INT BG;
将为pid_t PID;
INT状态;
结构statStuff试验;
int值; PID =叉（）;
如果（PID大于0）{
/ *这是父进程。 * /
字符* P;
INT n_bytes = 256;
INT bytes_read缓存;
字符缓冲区[256]; 的printf（父进程1 \\ n）;
//而（！（*值））{
//
//}
睡眠（2）;
的printf（父进程2 \\ n）; sem_getvalue（SEM，＆安培;值）;
sprintf的（缓冲的/ proc /％D /图，价值）;
的printf（缓冲=％S \\ n，缓冲区）;
INT FD =开放（缓冲，O_RDONLY）;
的printf（FD =％d个\\ N，FD）;
P =（字符*）malloc的（256）;
而（bytes_read缓存=读（FD，P，n_bytes））{
//输出（STRING =％S \\ n，p）的;
//打破;
如果（的strstr（P[堆]）！= NULL）{
的printf（％S \\ n，p）的;
}
自由（对）;
P =（字符*）malloc的（256）;
//了lseek（FD，256，SEEK_CUR）;
}
waitpid函数（PID，和放大器;状态，0）;
// EXECL（外壳，外壳 - C，CMDLINE，NULL）;
/ *
memset的（安培;测试，0的sizeof（结构statStuff））;
readStat（PID，和放大器;测试）;
// _exit（EXIT_FAILURE）;
* /
}
否则如果（PID℃，）{
/ *叉失败。报告故障。 * /
状态= -1;
}
其他{
的printf（BOO \\ n！）;
SEM = sem_open（统筹局常任秘书长，O_CREAT | O_EXCL，PID）;
的printf（FOO \\ n！）;
// sem_unlink（PSEM）;
的printf（你好\\ n）;
//的printf（ERROR =％d个\\ N，
execl的（/小时/ fchang03，/小时/ fchang03 /二，0）;
PERROR（execl的）;
}
}INT主要（无效）
{
烧焦CMDLINE [MAXLINE]
焦温度[MAXLINE] shmkey = ftok（的/ dev / null的，5）;
的shmid = shmget的（shmkey，sizeof的（INT），0644 | IPC_CREAT）;
如果（的shmid℃，）{
PERROR（shmget的\\ n）;
出口（1）;
} p值=（INT *）的shmat（的shmid，NULL，0）;
* p值= 0; 而（1）{
的printf（＆gt;中）;
与fgets（温度，MAXLINE，标准输入）;
sprintf的（CMDLINE./%的，温度）;
如果（的feof（标准输入））{
出口（0）;
}
的printf（CMDLINE =％S \\ n，CMDLINE）;
的eval（CMDLINE）;
} shmdt（P）;
了shmctl（的shmid，IPC_RMID，0）; sem_destroy（SEM）;
出口（0）;
}
解决方案
这行
EXECL（/ H / fchang03，/ H / fchang03 /二，0）;
建议你试图执行一个目录。
For the following C program, execl returns -1, signifying a Permission Denied error. I checked the read,write. execute permissions of my executables and they were all rwx. Could someone please let me know why execl is returning a Permission Denied error? Thank you very much
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/shm.h>
#include <errno.h>
#include <semaphore.h>
#define MAXLINE 256
#define MAXARGS 128
#define SHELL "/h/fchang03" // "/bin/sh"
key_t shmkey;
int shmid;
sem_t *sem;
int* p;
struct statStuff {
int pid; // %d
char comm[256]; // %s
char state; // %c
int ppid; // %d
int pgrp; // %d
int session; // %d
int tty_nr; // %d
int tpgid; // %d
unsigned long flags; // %lu
unsigned long minflt; // %lu
unsigned long cminflt; // %lu
unsigned long majflt; // %lu
unsigned long cmajflt; // %lu
unsigned long utime; // %lu
unsigned long stime; // %lu
long cutime; // %ld
long cstime; // %ld
long priority; // %ld
long nice; // %ld
long num_threads; // %ld
long itrealvalue; // %ld
unsigned long starttime; // %lu
unsigned long vsize; // %lu
long rss; // %ld
unsigned long rlim; // %lu
unsigned long startcode; // %lu
unsigned long endcode; // %lu
unsigned long startstack; // %lu
unsigned long kstkesp; // %lu
unsigned long kstkeip; // %lu
unsigned long signal; // %lu
unsigned long blocked; // %lu
unsigned long sigignore; // %lu
unsigned long sigcatch; // %lu
unsigned long wchan; // %lu
unsigned long nswap; // %lu
unsigned long cnswap; // %lu
int exit_signal; // %d
int processor; // %d
unsigned long rt_priority; // %lu
unsigned long policy; // %lu
unsigned long long delayacct_blkio_ticks; // %llu
} ;
static int readStat(int pid, struct statStuff *s) {
const char *format = "%d %s %c %d %d %d %d %d %lu %lu %lu %lu %lu %lu %lu %ld %ld %ld %ld %ld %ld %lu %lu %ld %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %d %d %lu %lu %llu";
char buf[256];
FILE *proc;
sprintf(buf,"/proc/%d/stat",pid);
proc = fopen(buf,"r");
if (proc) {
if (42==fscanf(proc, format,
&s->pid,
s->comm,
&s->state,
&s->ppid,
&s->pgrp,
&s->session,
&s->tty_nr,
&s->tpgid,
&s->flags,
&s->minflt,
&s->cminflt,
&s->majflt,
&s->cmajflt,
&s->utime,
&s->stime,
&s->cutime,
&s->cstime,
&s->priority,
&s->nice,
&s->num_threads,
&s->itrealvalue,
&s->starttime,
&s->vsize,
&s->rss,
&s->rlim,
&s->startcode,
&s->endcode,
&s->startstack,
&s->kstkesp,
&s->kstkeip,
&s->signal,
&s->blocked,
&s->sigignore,
&s->sigcatch,
&s->wchan,
&s->nswap,
&s->cnswap,
&s->exit_signal,
&s->processor,
&s->rt_priority,
&s->policy,
&s->delayacct_blkio_ticks
)) {
printf("Stack start = %x\n",s->startstack);
printf("Stack end = %x\n",s->kstkesp);
fclose(proc);
return 1;
} else {
fclose(proc);
return 0;
}
} else {
return 0;
}
}
int eval(const char *cmdline)
{
char *argv[MAXARGS];
int bg;
pid_t pid;
int status;
struct statStuff test;
int value;
pid = fork();
if (pid > 0){
/* This is the parent process. */
char* p;
int n_bytes = 256;
int bytes_read;
char buffer[256];
printf("PARENT PROCESS 1\n");
// while (!(*value)){
//
// }
sleep(2);
printf("PARENT PROCESS 2\n");
sem_getvalue(sem, &value);
sprintf(buffer,"/proc/%d/maps",value);
printf("buffer = %s\n",buffer);
int fd = open(buffer,O_RDONLY);
printf("fd = %d\n",fd);
p = (char *)malloc(256);
while (bytes_read = read(fd,p,n_bytes)){
//printf("STRING = %s\n",p);
//break;
if (strstr(p,"[heap]") != NULL){
printf("%s\n",p);
}
free(p);
p = (char *)malloc(256);
// lseek(fd,256,SEEK_CUR);
}
waitpid(pid, &status, 0);
// execl(SHELL,SHELL,"-c",cmdline,NULL);
/*
memset(&test, 0, sizeof(struct statStuff));
readStat(pid, &test);
// _exit(EXIT_FAILURE);
*/
}
else if (pid < 0){
/* The fork failed. Report failure. */
status = -1;
}
else{
printf("BOO!\n");
sem = sem_open("pSem", O_CREAT | O_EXCL, pid);
printf("FOO!\n");
// sem_unlink("pSem");
printf("HOWDY\n");
// printf("ERROR = %d\n",
execl("/h/fchang03","/h/fchang03/two",0);
perror("execl");
}
}
int main(void)
{
char cmdline[MAXLINE];
char temp[MAXLINE];
shmkey = ftok("/dev/null",5);
shmid = shmget(shmkey, sizeof (int), 0644 | IPC_CREAT);
if (shmid < 0){
perror("shmget\n");
exit(1);
}
p = (int *)shmat(shmid, NULL, 0);
*p = 0;
while (1){
printf("> ");
fgets(temp, MAXLINE, stdin);
sprintf(cmdline,"./%s",temp);
if (feof(stdin)){
exit(0);
}
printf("cmdline = %s\n",cmdline);
eval(cmdline);
}
shmdt(p);
shmctl(shmid, IPC_RMID, 0);
sem_destroy(sem);
exit(0);
}
解决方案
This line
execl("/h/fchang03","/h/fchang03/two",0);
suggests that you are trying to execute a directory.
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