我试图从用户获得一些数据,并将其发送到gcc中的另一个函数。代码是这样的。
printf("Enter your Name: ");
if (!(fgets(Name, sizeof Name, stdin) != NULL)) {
fprintf(stderr, "Error reading Name.\n");
exit(1);
}
然而,我发现它最后有一个换行符\n字符。如果我输入John,它最终会发送John\n。我如何删除\n并发送一个合适的字符串。
我试图从用户获得一些数据,并将其发送到gcc中的另一个函数。代码是这样的。
printf("Enter your Name: ");
if (!(fgets(Name, sizeof Name, stdin) != NULL)) {
fprintf(stderr, "Error reading Name.\n");
exit(1);
}
然而,我发现它最后有一个换行符\n字符。如果我输入John,它最终会发送John\n。我如何删除\n并发送一个合适的字符串。
当前回答
如果可以选择使用getline(不要忽略其安全性问题),如果希望使用大括号指针,则可以避免使用字符串函数,因为getline返回的是字符数。如下图所示
#include <stdio.h>
#include <stdlib.h>
int main()
{
char *fname, *lname;
size_t size = 32, nchar; // Max size of strings and number of characters read
fname = malloc(size * sizeof *fname);
lname = malloc(size * sizeof *lname);
if (NULL == fname || NULL == lname)
{
printf("Error in memory allocation.");
exit(1);
}
printf("Enter first name ");
nchar = getline(&fname, &size, stdin);
if (nchar == -1) // getline return -1 on failure to read a line.
{
printf("Line couldn't be read..");
// This if block could be repeated for next getline too
exit(1);
}
printf("Number of characters read :%zu\n", nchar);
fname[nchar - 1] = '\0';
printf("Enter last name ");
nchar = getline(&lname, &size, stdin);
printf("Number of characters read :%zu\n", nchar);
lname[nchar - 1] = '\0';
printf("Name entered %s %s\n", fname, lname);
return 0;
}
注意:getline的[安全问题]不应该被忽视。
其他回答
下面是一个从fgets()保存的字符串中删除潜在'\n'的快速方法。 它使用strlen(),带有2个测试。
char buffer[100];
if (fgets(buffer, sizeof buffer, stdin) != NULL) {
size_t len = strlen(buffer);
if (len > 0 && buffer[len-1] == '\n') {
buffer[--len] = '\0';
}
现在根据需要使用buffer和len。
该方法的附带好处是为后续代码提供len值。它可以比strchr(Name, '\n')更快。参考YMMV,但两种方法都有效。
在某些情况下,原始fgets()将不包含在"\n"中: A)行太长,不适合buffer,所以只有'\n'前面的char被保存在buffer中。未读字符保留在流中。 B)文件的最后一行没有以“\n”结尾。
如果输入在某个地方嵌入了空字符'\0',strlen()报告的长度将不包括'\n'位置。
其他一些回答的问题:
strtok(buffer, "\n"); fails to remove the '\n' when buffer is "\n". From this answer - amended after this answer to warn of this limitation. The following fails on rare occasions when the first char read by fgets() is '\0'. This happens when input begins with an embedded '\0'. Then buffer[len -1] becomes buffer[SIZE_MAX] accessing memory certainly outside the legitimate range of buffer. Something a hacker may try or found in foolishly reading UTF16 text files. This was the state of an answer when this answer was written. Later a non-OP edited it to include code like this answer's check for "". size_t len = strlen(buffer); if (buffer[len - 1] == '\n') { // FAILS when len == 0 buffer[len -1] = '\0'; } sprintf(buffer,"%s",buffer); is undefined behavior: Ref. Further, it does not save any leading, separating or trailing whitespace. Now deleted. [Edit due to good later answer] There are no problems with the 1 liner buffer[strcspn(buffer, "\n")] = 0; other than performance as compared to the strlen() approach. Performance in trimming is usually not an issue given code is doing I/O - a black hole of CPU time. Should following code need the string's length or is highly performance conscious, use this strlen() approach. Else the strcspn() is a fine alternative.
如果每一行都有'\n',则直接从fgets输出中删除'\n'
line[strlen(line) - 1] = '\0';
否则:
void remove_newline_ch(char *line)
{
int new_line = strlen(line) -1;
if (line[new_line] == '\n')
line[new_line] = '\0';
}
for(int i = 0; i < strlen(Name); i++ )
{
if(Name[i] == '\n') Name[i] = '\0';
}
你应该试试。这段代码基本上遍历字符串,直到找到'\n'。当它被找到时,'\n'将被空字符结束符'\0'取代
注意,在这一行中比较的是字符而不是字符串,那么就不需要使用strcmp():
if(Name[i] == '\n') Name[i] = '\0';
因为你将使用单引号而不是双引号。如果你想了解更多,这里有一个关于单引号和双引号的链接
对于单个“\n”切边,
void remove_new_line(char* string)
{
size_t length = strlen(string);
if((length > 0) && (string[length-1] == '\n'))
{
string[length-1] ='\0';
}
}
对于多个“\n”切边,
void remove_multi_new_line(char* string)
{
size_t length = strlen(string);
while((length>0) && (string[length-1] == '\n'))
{
--length;
string[length] ='\0';
}
}
Tim Čas one line对于调用fgets获得的字符串来说非常神奇,因为您知道它们在末尾包含一个换行符。
如果您处于不同的上下文中,并且希望处理可能包含多个换行符的字符串,则可能需要查找strrspn。它不是POSIX,这意味着您不会在所有unix上找到它。我为自己的需要写了一个。
/* Returns the length of the segment leading to the last
characters of s in accept. */
size_t strrspn (const char *s, const char *accept)
{
const char *ch;
size_t len = strlen(s);
more:
if (len > 0) {
for (ch = accept ; *ch != 0 ; ch++) {
if (s[len - 1] == *ch) {
len--;
goto more;
}
}
}
return len;
}
对于那些在C中寻找等效Perl chomp的人来说,我认为这就是它(chomp只删除后面的换行符)。
line[strrspn(string, "\r\n")] = 0;
strrcspn函数:
/* Returns the length of the segment leading to the last
character of reject in s. */
size_t strrcspn (const char *s, const char *reject)
{
const char *ch;
size_t len = strlen(s);
size_t origlen = len;
while (len > 0) {
for (ch = reject ; *ch != 0 ; ch++) {
if (s[len - 1] == *ch) {
return len;
}
}
len--;
}
return origlen;
}