提供代码 M.R.E。
症状是“简单”:
hello\nhello\nhelloEOF 并插入 '_' @ ln=2 & col=1 (或者更确切地说是任何 line>1 && col==1)程序奇怪地做对了，但是吃掉了 '\n' ，导致第 2 行与第 1 行 融合 - hello_hello\nhelloEOF，而不是 hello\n_hello\nhelloEOF。hello\nhello\nhelloEOF 的最后一行中插入 '_' @ ln=3 & col=5(或者更确切地说，在由 EOF 终止的行中的任何字符 col>1)导致它跳过最后一个实际字符行:hello\nhello\nhell_EOF 而不是 hello\nhello\nhell_oEOF。col==1 in line terminated by EOF)导致错误消息(\n Invalid Index.)扔了。就我的直觉而言，我认为在处理行终止 ('\n',EOF) 及其计算方式时存在缺陷通常作为循环计数器，但我不明白。
想法/算法:
EOF。下面的代码完成了所有真正的对话:
#include <stdio.h>
#include <string.h>
/* Likely error region in chknmove(), chkncpy() and/or main() ;
All other functions used are also provided */
long long lncnt(FILE *lcount){
/* counts the number of lines in a file with fgets() */
rewind(lcount); /* ensures lines counted from beginning */
long long lines=0; char line[501];
while((fgets(line,501,lcount))!=NULL){
lines++;
}
rewind(lcount); /* leaves fptr @ 0,0 rather than EOF */
return lines;
}
int chknmove(FILE *tomove, long long line, long long col){
/* Function to check & move FILE* to certain line/col */
rewind(tomove); /* make sure fptr is at beginning of file */
int f=0; /* set check-variable to 0 for successful */
if(line<1 || col<1)
f = -1; /* Ln,col cannot be -ve or even 0 -> 1st col is @ 1ln,1col in any non-empty file */
else{
long long i,q; i=1;q=0; /* i = lines seen, q = cols seen */
/* i init to 1 for ease of comprehension v/s testing 'line-1' */
while(i<line || q<col){ /* loop must iterate until i==line && q==col */
int ch = fgetc(tomove); /* int to store EOF */
if(ch==EOF){
f=-1; break; /* if file ends before reaching index, failed. */
}
else if(ch=='\n') {
if(i==line){
f=-1; break;/* if line ends before reaching col in ln, failed. */
}
i++; q=0; /* else , increase i by 1 and set q (col) to 0 */
}
else
q++; /* any other character is 'normal' , just increment q (col) by 1 */
}
}
if(f==0){
fseek(tomove,-1,SEEK_CUR);
/* since index must be checked, loop reaches it -> fseek(-1) causes *next* r/w to fptr to be on the index . */
return 0;
}
else{
/* f != 0 : moving has failed. */
printf("\n Invalid Index.\n");
return -1;
}
}
int chkncpy(FILE *source, FILE *dest,long long beginln, long long begincol, long long endln, long long endcol){
rewind(source); int f=0;
if(beginln<1 || begincol<1 || endln<beginln || endcol<1 || (beginln==endln && endcol<begincol))
f=-1; /* line/col must be >= 1 in non-empty file, copying done top to bottom (begin-index <= end-index ) */
else{
if(chknmove(source,beginln,begincol)==0){
/* loop begins if begin-index is valid */
long long i,q; i=beginln;q=begincol; /* i = lines, q = cols */
while(i<endln || q<endcol){
/* while end-index is not reached : !(i==endln && q==endcol) */
int ch = fgetc(source);
if(ch==EOF) {f=-1; break;} /* File ends b/w begin-index & end-index - failed. */
else if(ch=='\n') {
if(i==endln) {f=-1; break;} /* endln ends before reaching endcol - failed */
i++; q=0;
fputc(ch,dest); /* valid '\n' put in dest file */
}
else{
q++; fputc(ch,dest); /* valid char put in dest file */
}
}
}
else f=-1; /* if begin-index is invalid, failed. */
}
if(f==-1){
/* if f != 0 : chkncpy() failed */
printf("\n Invalid Index.\n");
return -1;
}
else /* if f remains == 0 */ return 0;
}
long long lastlncol(FILE *fyl){
rewind(fyl); /* makes sure fptr @ beginning */
chknmove(fyl,lncnt(fyl),1); /* move to last line */
long long cnt=0; /* cnt stores no. of chars in last line */
while(1){
int g = fgetc(fyl);
if (g==EOF)
break; /* EOF not counted */
else if(g=='\n'){
cnt++;break; /* \n is counted as a char, but also as EOL */
}
else
cnt++; /* all other chars counted */
}
rewind(fyl); /* leaves file at its beginning */
return cnt;
}
long long lcc(FILE *fyl,long long line){
rewind(fyl); int f = chknmove(fyl,line,1); /* moves fptr to line */
long long cnt=0;
if(f==0){
while(1){
int g = fgetc(fyl);
if (g==EOF)
break;
else if(g=='\n'){
cnt++;break;
}
else
cnt++;
}
rewind(fyl);
return cnt;
}
else
return -1;
}
void writer(FILE *write, int ctrl){
printf("\n Terminate Input with \"/end/\".\n\n Type below :\n\n");
char in[501]; /* str that stores input line-by-line */
char *p; int o;
while(1){
fgets(in,501,stdin); /* takes line from user */
if((p=strstr(in,"/end/"))!=0){
/* if line has "/end/", all chars till /end/ are written to file and input loop breaks */
o = p-in;
fprintf(write,"%.*s",o,in);
break;
}
else{
/* writes line to file */
fputs(in,write);
}
}
if(ctrl==0){
/* in some cases, file must not be closed yet , hence ctrl is taken */
int s = fclose(write);
if(s==EOF) printf("\n Error ");
else printf("\n Success.\n");
}
}
void eat() /* clears stdin */
{
int eat;while ((eat = getchar()) != '\n' && eat != EOF);
}
int main(){
/* main to add/insert to file @ given index */
char fadd[501];/* filename str */
printf("\n Filename : "); scanf("%500[^\n]",fadd);
FILE * add = fopen(fadd,"r");
if(add==NULL)
perror("\n Error "); /* if file does not pre-exist */
else{
long long line, col; char sep; printf("\n Index : "); scanf("%lld%c%lld",&line,&sep,&col); /* takes index in ln-char-col form */
eat(); /* clears stdin */
FILE * tmp=fopen("Temp.Ctt","w"); /* opens a tmp file to write */
if(tmp==NULL)
perror("\n Error "); /* failed - tmp file could not be created to write */
else{
int f; /* success var */
if(line==1 && col>1){
/* if user wants to insert @ a col>1 in line 1 */
f = chkncpy(add,tmp,1,1,line,col); /* all below calls intend to write till 1 char before the char @ given index */
}
else if(line>1 && col>1){
/* if user wants to insert @ a col>1 in any line>1*/
f = chkncpy(add,tmp,1,1,line,col-1);
}
else if(line>1 && col==1){ //ERRORS - ignores the '\n' of line-1
/* if user wants to insert @ a 1st col in line>1 */
f = chkncpy(add,tmp,1,1,line-1,lcc(add,line-1));
}
else if(line==1 && col==1){
/* if user wants to insert @ 1,1 (no moving/copying needed) */
f=0;
}
else{
printf("\n Invalid Index.\n");f=-1;
}
if(f==0){
writer(tmp,1);
/* calls function to allow user to write to fptr , with ctrl != 0, so writer() *won't* fclose(tmp) */
chkncpy(add,tmp,line,col,lncnt(add),lastlncol(add));
/* copies all characters from index till EOF */
int ok = fclose(tmp); fclose(add);
if(ok==EOF){
/* if closing tmp was unsuccessful, the file on disk may be corrupted/incomplete, so must be removed */
remove("Temp.Ctt");perror("\n Error ");
}
else{
if(rename("Temp.Ctt",fadd)==0)
printf("\n Success.\n");
else{
/* on Windows & some other non-POSIX systems, file cannot be renamed to pre-existing filename , hence delete original */
remove(fadd);
if(rename("Temp.Ctt",fadd)==0)
printf("\n Success.\n");
else{
/* if rename still unsuccessful, throw an error, remove tmp file and give up */
remove("Temp.Ctt");
perror("\n Error ");
}
}
}
}
}
}
}
如果有任何遗漏的细节或无意的错误，请发表评论，我会更正它们。
最佳答案
你的代码太复杂了:
复制文件开头的不同情况应该合并到一个函数调用中，该函数调用将数据复制到并排除 col 行 line.
然后您从用户输入中复制。
最后复制输入文件的其余部分。
代码假定行和列从 1 开始编号。这可能是显而易见的，但您应该具体说明这一点，因为它可能对每个人来说都不是显而易见的。
这种风格很难阅读:你应该在二元运算符周围使用水平空间，在关键字、、 和 ; 之后和 {。在一行中塞满多个语句也不是一个好主意。
这是一个简化版本。通常，大部分代码用于错误处理:
#include <stdio.h>
#include <string.h>
void flush_line(FILE *fp) { /* read the rest of the current line */
int c;
while ((c = getc(fp)) != '\n' && c != EOF)
continue;
}
int copy_file(FILE *from, FILE *to) {
int c;
while ((c = getc(from)) != EOF) {
if (putc(c, to) == EOF)
return EOF;
}
return 0;
}
int copy_lines(FILE *from, int line1, int col1, FILE *to) {
int c, line = 1, col = 1;
for (;;) {
if (line >= line1 || (line == line1 && col >= col1))
break;
if ((c = getc(from)) == EOF)
break;
if (putc(c, to) == EOF)
return EOF;
col++;
if (c == '\n') {
line++;
col = 1;
}
}
return 0;
}
int writer(FILE *write) {
char in[501]; /* str that stores input line-by-line */
char *p;
printf("\n Terminate Input with \"/end/\".\n\n Type below :\n\n");
while (fgets(in, 501, stdin)) {
if ((p = strstr(in, "/end/")) != NULL) {
/* if line has "/end/", all chars till /end/ are written to file and input loop breaks */
int o = p - in;
if (fprintf(write, "%.*s", o, in) < 0)
return EOF;
break;
} else {
/* writes line to file */
if (fputs(in, write) < 0)
return EOF;
}
}
return 0;
}
int main() {
/* main to add/insert to file @ given index */
const char *temp_filename = "Temp.Ctt";
char fadd[501];/* filename str */
printf("\n Filename : ");
if (scanf("%500[^\n]", fadd) != 1)
return 1;
flush_line(stdin);
FILE *add = fopen(fadd, "r");
if (add == NULL) {
perror("\n Cannot open input file");
return 1;
}
int line, col;
/* read the index: 1 based line and column numbers */
printf("\n Index : ");
if (scanf("%d%*c%d", &line, &col) != 2) {
fprintf(stderr, "invalid input\n");
return 1;
}
flush_line(stdin);
FILE *tmp = fopen(temp_filename, "w");
if (tmp == NULL) {
perror("\n Cannot create temporary file");
fclose(add);
return 1;
}
if (copy_lines(add, line, col, tmp)) {
perror("\n Error copying beginning of file");
fclose(add);
fclose(tmp);
remove(temp_filename);
return 1;
}
if (writer(tmp)) {
perror("\n Error writing user input");
fclose(add);
fclose(tmp);
remove(temp_filename);
return 1;
}
if (copy_file(add, tmp)) {
perror("\n Error copying remaining file contents");
fclose(add);
fclose(tmp);
remove(temp_filename);
return 1;
}
fclose(add);
if (fclose(tmp) < 0) {
/* if closing tmp was unsuccessful, the file on disk may be corrupted/incomplete, so must be removed */
perror("\n Error closing temporary file");
remove(temp_filename);
return 1;
}
if (rename(temp_filename, fadd) == 0) {
printf("\n Success.\n");
return 0;
}
/* on Windows & some other non-POSIX systems, file cannot be renamed to pre-existing filename , hence delete original */
if (remove(fadd)) {
perror("\n Cannot remove input file");
remove(temp_filename);
return 1;
}
if (rename(temp_filename, fadd) == 0) {
printf("\n Success.\n");
return 1;
}
/* if rename still unsuccessful, try and copy contents */
tmp = fopen(temp_filename, "r");
if (tmp == NULL) {
perror("\n Cannot re-open temporary file, output is in Temp.Ctt");
return 1;
}
add = fopen(fadd, "w");
if (add == NULL) {
perror("\n Cannot re-open input file, output is in Temp.Ctt");
fclose(tmp);
return 1;
}
if (copy_file(tmp, add)) {
perror("\n Error copying temporary file to input file");
fclose(add);
fclose(tmp);
return 1;
}
fclose(tmp);
if (fclose(add) < 0) {
perror("\n Error closing input file");
return 1;
}
/* throw an error, remove tmp file and give up */
remove(temp_filename);
printf("\n Success.\n");
return 0;
}
关于c - 尝试将 'insert' 或 'add' 写入文本文件 - 一个小问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/63756638/