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c - 标记字符串并将其作为数组返回

转载 作者:行者123 更新时间:2023-11-30 14:31:37 27 4
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我正在尝试对传递的字符串进行标记,将标记存储在数组中并返回它。我在 ubuntu 上运行这个。显然,当谈到这种语言时,我被难住了。

示例输入:coinflip 3

我的代码思考过程如下:

take: string
if string = null: return null
else:
while temp != null
token[i++] = temp
temp = get next token
return

这是我当前的解决方案。分隔符是空格。 C 语言已经不是我的强项有一段时间了。

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

//Clears the screen and prompts the user
void msg()
{
static int init = 1;
if(init)
{
printf("\e[1;1H\e[2J");
init = 0;
}
printf("%s", "uab_sh > ");

}

//Reads in line
char *readIn(void)
{
char param[101];
fgets(param, 101, stdin);
return param;
}

//parse string - still working out the kinks :)
char **parseString(char *cmd)
{
char delim[] = " ";
char* temp = strtok(cmd, delim);
if (temp == " ")
{
return NULL;
}
else
{
int i = 0;
char** tokens = malloc(3 * sizeof(char*));
while (temp != NULL)
{
tokens[i++] = temp;
temp = strtok(NULL, " ");
}
for (i = 0; i < 3; i++)
{
printf("%s\n", tokens[i]);
}
return tokens;
}
}

//Command
int command(char ** cmd)
{
int pid;
if (cmd[0] != NULL)
{
pid = fork();
if (pid == 0)
{
exit(0);
}
else if (pid < 0)
{
perror("Something went wrong...");
}
}
else
return 1;
}


int main()
{
char *line;
char **cmd;
int stat = 0;
while (1)
{
msg();
line = readLine();
cmd = parseString(line);
stat = command(cmd);
if (stat == 1)
{
break;
}
}
return 0;
}

当前错误:

main.c: In function ‘readIn’:
main.c:24:9: warning: function returns address of local variable [-Wreturn-local-addr]
return param;
^~~~~
main.c: In function ‘parseString’:
main.c:32:11: warning: comparison with string literal results in unspecified behavior [-Waddress]
if (temp == " ")
^~
main.c: In function ‘command’:
main.c:59:9: warning: implicit declaration of function ‘fork’ [-Wimplicit-function-declaration]
pid = fork();
^~~~
main.c: In function ‘main’:
main.c:82:10: warning: implicit declaration of function ‘readLine’; did you mean ‘readIn’? [-Wimplicit-function-declaration]
line = readLine();
^~~~~~~~
readIn
main.c:82:8: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
line = readLine();
^
main.c: In function ‘command’:
main.c:71:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^

最佳答案

编译器已经报告该函数

//Read-in string
char *readIn(void)
{
char param[101];
fgets(param, 101, stdin);
return param;
}

具有未定义的行为,因为它返回指向本地数组param的指针,该数组在退出函数后将不存在。

在这个函数中

char *parseString(char* cmd)
{
char* temp = strtok(cmd, " ");
if (cmd == NULL)
{
return temp;
}
else
{
int i = 0;
char *tokens[3];
while (temp != NULL)
{
tokens[i++] = temp;
temp = strtok(NULL, " ");
}
for (i = 0; i < 3; i++)
{
printf("%s\n", tokens[i]);
}
return tokens;
}
}

存在同样的问题(如果不考虑错误的实现),而且返回表达式的类型

        return tokens;

与函数的返回类型不对应,因为return语句中的表达式的类型为char **,而函数的返回类型为char * .

我确信对您来说最困难的是编写将字符串拆分为标记的函数。

它可以如下所示,如下面的演示程序所示。该函数为指向标记的指针数组动态分配内存。如果分配失败该函数返回 NULL。否则,该函数返回指向动态分配的指针数组的第一个元素的指针。数组的最后一个元素包含 NULL。该元素可用于确定数组中指向标记的实际指针的数量。

给你。

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char ** parseString( char *cmd )
{
char **tokens = malloc( sizeof( char * ) );
*tokens = NULL;
size_t n = 1;

const char *delim = " \t";

char *p = strtok( cmd, delim );

int success = p != NULL;

while ( success )
{
char **tmp = realloc( tokens, ( n + 1 ) * sizeof( char * ) );

if ( tmp == NULL )
{
free( tokens );
tokens = NULL;

success = 0;
}
else
{
tokens = tmp;

tokens[n - 1] = p;
tokens[n] = NULL;
++n;

p = strtok( NULL, delim );

success = p != NULL;
}
}

return tokens;
}

int main(void)
{
char cmd[] = "Many various and unique commands";

char **tokens = parseString( cmd );

if ( tokens != NULL )
{
for ( char **p = tokens; *p != NULL; ++p )
{
puts( *p );
}
}

free( tokens );

return 0;
}

程序输出为

Many
various
and
unique
commands

关于c - 标记字符串并将其作为数组返回,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/60218137/

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