user-0 提问: linux 下fopen打开文件失败

回复:
user: user-1
content: 引用 5 楼 user-4 的回复:file_name = "./fileptr.c"; /*文件路径*/ 编译能过吗？应该是strcpy(file_name, "./fileptr.c");吧 5楼正确

user: user-2
content: 引用 8 楼 zcmerlin 的回复:[quote=引用 6 楼 cfjtaishan 的回复:] 我看原因是这个：file_name = "fileptr.c" 文件名没有./，把文件名的./去掉；程序在当前目录下找文件名是./fileptr.c，但是该文件应该不存在的。 引用 6 楼 cfjtaishan 的回复:我看原因是这个：file_name = "fileptr.c" 文件名没有./，把文件名的./去掉；程序在当前目录下找文件名是./fileptr.c，但是该文件应该不存在的。  那样没问题的[/quote] 没问题吗？

user: user-0
content: 引用 11 楼 zhao4zhong1 的回复:strerror, _strerror Get a system error message (strerror) or prints a user-supplied error message (_strerror).  char *strerror( int errnum );  char *_strerror( const char *strErrMsg );  Routine Required Header Compatibility  strerror <string.h> ANSI, Win 95, Win NT  _strerror <string.h> Win 95, Win NT    For additional compatibility information, see Compatibility in the Introduction.  Libraries  LIBC.LIB Single thread static library, retail version  LIBCMT.LIB Multithread static library, retail version  MSVCRT.LIB Import library for MSVCRT.DLL, retail version    Return Value  strerror and _strerror return a pointer to the error-message string. Subsequent calls to strerror or _strerror can overwrite the string.  Parameters  errnum  Error number  strErrMsg  User-supplied message  Remarks  The strerror function maps errnum to an error-message string, returning a pointer to the string. Neither strerror nor _strerror actually prints the message: For that, you need to call an output function such as fprintf:  if (( _access( "datafile",2 )) == -1 )    fprintf( stderr, strerror(NULL) );  If strErrMsg is passed as NULL, _strerror returns a pointer to a string containing the system error message for the last library call that produced an error. The error-message string is terminated by the newline character ('\n'). If strErrMsg is not equal to NULL, then _strerror returns a pointer to a string containing (in order) your string message, a colon, a space, the system error message for the last library call producing an error, and a newline character. Your string message can be, at most, 94 bytes long.  The actual error number for _strerror is stored in the variable errno. The system error messages are accessed through the variable _sys_errlist, which is an array of messages ordered by error number. _strerror accesses the appropriate error message by using the errno value as an index to the variable _sys_errlist. The value of the variable _sys_nerr is defined as the maximum number of elements in the _sys_errlist array. To produce accurate results, call _strerror immediately after a library routine returns with an error. Otherwise, subsequent calls to strerror or _strerror can overwrite the errno value.  _strerror is not part of the ANSI definition but is instead a Microsoft extension to it. Do not use it where portability is desired; for ANSI compatibility, use strerror instead.  Example  /* PERROR.C: This program attempts to open a file named  * NOSUCHF.ILE. Because this file probably doesn't exist,  * an error message is displayed. The same message is  * created using perror, strerror, and _strerror.  */  #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #include <io.h> #include <stdlib.h> #include <stdio.h> #include <string.h>  void main( void ) {    int  fh;     if( (fh = _open( "NOSUCHF.ILE", _O_RDONLY )) == -1 )    {       /* Three ways to create error message: */       perror( "perror says open failed" );       printf( "strerror says open failed: %s\n", strerror( errno ) );       printf( _strerror( "_strerror says open failed" ) );    }    else    {       printf( "open succeeded on input file\n" );       _close( fh );    } }   Output  perror says open failed: No such file or directory  strerror says open failed: No such file or directory _strerror says open failed: No such file or directory   String Manipulation Routines  See Also   clearerr, ferror, perror   多谢，问题已经解决，step进不到fopen里

user: user-3
content: strerror, _strerror Get a system error message (strerror) or prints a user-supplied error message (_strerror).  char *strerror( int errnum );  char *_strerror( const char *strErrMsg );  Routine Required Header Compatibility  strerror <string.h> ANSI, Win 95, Win NT  _strerror <string.h> Win 95, Win NT    For additional compatibility information, see Compatibility in the Introduction.  Libraries  LIBC.LIB Single thread static library, retail version  LIBCMT.LIB Multithread static library, retail version  MSVCRT.LIB Import library for MSVCRT.DLL, retail version    Return Value  strerror and _strerror return a pointer to the error-message string. Subsequent calls to strerror or _strerror can overwrite the string.  Parameters  errnum  Error number  strErrMsg  User-supplied message  Remarks  The strerror function maps errnum to an error-message string, returning a pointer to the string. Neither strerror nor _strerror actually prints the message: For that, you need to call an output function such as fprintf:  if (( _access( "datafile",2 )) == -1 )    fprintf( stderr, strerror(NULL) );  If strErrMsg is passed as NULL, _strerror returns a pointer to a string containing the system error message for the last library call that produced an error. The error-message string is terminated by the newline character ('\n'). If strErrMsg is not equal to NULL, then _strerror returns a pointer to a string containing (in order) your string message, a colon, a space, the system error message for the last library call producing an error, and a newline character. Your string message can be, at most, 94 bytes long.  The actual error number for _strerror is stored in the variable errno. The system error messages are accessed through the variable _sys_errlist, which is an array of messages ordered by error number. _strerror accesses the appropriate error message by using the errno value as an index to the variable _sys_errlist. The value of the variable _sys_nerr is defined as the maximum number of elements in the _sys_errlist array. To produce accurate results, call _strerror immediately after a library routine returns with an error. Otherwise, subsequent calls to strerror or _strerror can overwrite the errno value.  _strerror is not part of the ANSI definition but is instead a Microsoft extension to it. Do not use it where portability is desired; for ANSI compatibility, use strerror instead.  Example  /* PERROR.C: This program attempts to open a file named  * NOSUCHF.ILE. Because this file probably doesn't exist,  * an error message is displayed. The same message is  * created using perror, strerror, and _strerror.  */  #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #include <io.h> #include <stdlib.h> #include <stdio.h> #include <string.h>  void main( void ) {    int  fh;     if( (fh = _open( "NOSUCHF.ILE", _O_RDONLY )) == -1 )    {       /* Three ways to create error message: */       perror( "perror says open failed" );       printf( "strerror says open failed: %s\n", strerror( errno ) );       printf( _strerror( "_strerror says open failed" ) );    }    else    {       printf( "open succeeded on input file\n" );       _close( fh );    } }   Output  perror says open failed: No such file or directory  strerror says open failed: No such file or directory _strerror says open failed: No such file or directory   String Manipulation Routines  See Also   clearerr, ferror, perror

user: user-3
content: errno shall be set to indicate the error

user: user-0
content: 引用 2 楼 zhao4zhong1 的回复:FOPEN Section: POSIX Programmer's Manual (P) Updated: 2003  --------------------------------------------------------------------------------    NAME fopen - open a stream    SYNOPSIS #include <stdio.h>     FILE *fopen(const char *restrict filename, const char *restrict mode);      DESCRIPTION The fopen() function shall open the file whose pathname is the string pointed to by filename, and associates a stream with it.   The mode argument points to a string. If the string is one of the following, the file shall be opened in the indicated mode. Otherwise, the behavior is undefined.   r or rb Open file for reading.  w or wb Truncate to zero length or create file for writing.  a or ab Append; open or create file for writing at end-of-file.  r+ or rb+ or r+b Open file for update (reading and writing).  w+ or wb+ or w+b Truncate to zero length or create file for update.  a+ or ab+ or a+b Append; open or create file for update, writing at end-of-file.   The character 'b' shall have no effect, but is allowed for ISO C standard conformance. Opening a file with read mode (r as the first character in the mode argument) shall fail if the file does not exist or cannot be read.   Opening a file with append mode (a as the first character in the mode argument) shall cause all subsequent writes to the file to be forced to the then current end-of-file, regardless of intervening calls to fseek().   When a file is opened with update mode ( '+' as the second or third character in the mode argument), both input and output may be performed on the associated stream. However, the application shall ensure that output is not directly followed by input without an intervening call to fflush() or to a file positioning function ( fseek(), fsetpos(), or rewind()), and input is not directly followed by output without an intervening call to a file positioning function, unless the input operation encounters end-of-file.   When opened, a stream is fully buffered if and only if it can be determined not to refer to an interactive device. The error and end-of-file indicators for the stream shall be cleared.   If mode is w, wb, a, ab, w+, wb+, w+b, a+, ab+, or a+b, and the file did not previously exist, upon successful completion, the fopen() function shall mark for update the st_atime, st_ctime, and st_mtime fields of the file and the st_ctime and st_mtime fields of the parent directory.   If mode is w, wb, w+, wb+, or w+b, and the file did previously exist, upon successful completion, fopen() shall mark for update the st_ctime and st_mtime fields of the file. The fopen() function shall allocate a file descriptor as open() does.   After a successful call to the fopen() function, the orientation of the stream shall be cleared,  the encoding rule shall be cleared, and the associated mbstate_t object shall be set to describe an initial conversion state.   The largest value that can be represented correctly in an object of type off_t shall be established as the offset maximum in the open file description.     RETURN VALUE Upon successful completion, fopen() shall return a pointer to the object controlling the stream. Otherwise, a null pointer shall be returned,  and errno shall be set to indicate the error.     ERRORS The fopen() function shall fail if:   EACCES  Search permission is denied on a component of the path prefix, or the file exists and the permissions specified by mode are denied, or the file does not exist and write permission is denied for the parent directory of the file to be created.  EINTR  A signal was caught during fopen().  EISDIR  The named file is a directory and mode requires write access.  ELOOP  A loop exists in symbolic links encountered during resolution of the path argument.  EMFILE  {OPEN_MAX} file descriptors are currently open in the calling process.  ENAMETOOLONG  The length of the filename argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.   ENFILE  The maximum allowable number of files is currently open in the system.  ENOENT  A component of filename does not name an existing file or filename is an empty string.  ENOSPC  The directory or file system that would contain the new file cannot be expanded, the file does not exist, and the file was to be created.  ENOTDIR  A component of the path prefix is not a directory.  ENXIO  The named file is a character special or block special file, and the device associated with this special file does not exist.  EOVERFLOW  The named file is a regular file and the size of the file cannot be represented correctly in an object of type off_t.  EROFS  The named file resides on a read-only file system and mode requires write access.   The fopen() function may fail if:   EINVAL  The value of the mode argument is not valid.  ELOOP  More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.  EMFILE  {FOPEN_MAX} streams are currently open in the calling process.  EMFILE  {STREAM_MAX} streams are currently open in the calling process.  ENAMETOOLONG  Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.   ENOMEM  Insufficient storage space is available.  ETXTBSY  The file is a pure procedure (shared text) file that is being executed and mode requires write access.   The following sections are informative.     EXAMPLES    Opening a File The following example tries to open the file named file for reading. The fopen() function returns a file pointer that is used in subsequent fgets() and fclose() calls. If the program cannot open the file, it just ignores it.     #include <stdio.h> ... FILE *fp; ... void rgrep(const char *file) { ...     if ((fp = fopen(file, "r")) == NULL)         return; ... }      APPLICATION USAGE None.     RATIONALE None.     FUTURE DIRECTIONS None.     SEE ALSO fclose() , fdopen() , freopen() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h>     COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .  --------------------------------------------------------------------------------  基本的使用会，现在遇到的情况是用gdb单步走时，就是帖子里遇到的情况，但直接运行编译好的程序没问题，也就是文件可以正常读取，这问题到底处在哪里呢

user: user-0
content: 引用 6 楼 cfjtaishan 的回复:我看原因是这个：file_name = "fileptr.c" 文件名没有./，把文件名的./去掉；程序在当前目录下找文件名是./fileptr.c，但是该文件应该不存在的。 引用 6 楼 cfjtaishan 的回复:我看原因是这个：file_name = "fileptr.c" 文件名没有./，把文件名的./去掉；程序在当前目录下找文件名是./fileptr.c，但是该文件应该不存在的。  那样没问题的

user: user-0
content: 引用 5 楼 user-4 的回复:file_name = "./fileptr.c"; /*文件路径*/ 编译能过吗？应该是strcpy(file_name, "./fileptr.c");吧 编译可以通过的

user: user-2
content: 我看原因是这个：file_name = "fileptr.c" 文件名没有./，把文件名的./去掉；程序在当前目录下找文件名是./fileptr.c，但是该文件应该不存在的。

user: user-4
content: file_name = "./fileptr.c"; /*文件路径*/ 编译能过吗？应该是strcpy(file_name, "./fileptr.c");吧

user: user-0
content: 引用 3 楼 cfjtaishan 的回复:没有那个文件或目录。错误信息已经打出来了。 另外，确认一下该文件是否和可执行程序在同一目录下    在同一个目录下的，本来不在同一个目录下，后来怕出错，就专门给同一目录下也放了一份源文件； 另，fopen后面有if判断文件打开是否成功，怎么都走不到if就报错了呢

user: user-2
content: 没有那个文件或目录。错误信息已经打出来了。 另外，确认一下该文件是否和可执行程序在同一目录下

user: user-3
content: FOPEN Section: POSIX Programmer's Manual (P) Updated: 2003  --------------------------------------------------------------------------------    NAME fopen - open a stream    SYNOPSIS #include <stdio.h>    FILE *fopen(const char *restrict filename, const char *restrict mode);      DESCRIPTION The fopen() function shall open the file whose pathname is the string pointed to by filename, and associates a stream with it.   The mode argument points to a string. If the string is one of the following, the file shall be opened in the indicated mode. Otherwise, the behavior is undefined.   r or rb Open file for reading.  w or wb Truncate to zero length or create file for writing.  a or ab Append; open or create file for writing at end-of-file.  r+ or rb+ or r+b Open file for update (reading and writing).  w+ or wb+ or w+b Truncate to zero length or create file for update.  a+ or ab+ or a+b Append; open or create file for update, writing at end-of-file.   The character 'b' shall have no effect, but is allowed for ISO C standard conformance. Opening a file with read mode (r as the first character in the mode argument) shall fail if the file does not exist or cannot be read.   Opening a file with append mode (a as the first character in the mode argument) shall cause all subsequent writes to the file to be forced to the then current end-of-file, regardless of intervening calls to fseek().   When a file is opened with update mode ( '+' as the second or third character in the mode argument), both input and output may be performed on the associated stream. However, the application shall ensure that output is not directly followed by input without an intervening call to fflush() or to a file positioning function ( fseek(), fsetpos(), or rewind()), and input is not directly followed by output without an intervening call to a file positioning function, unless the input operation encounters end-of-file.   When opened, a stream is fully buffered if and only if it can be determined not to refer to an interactive device. The error and end-of-file indicators for the stream shall be cleared.   If mode is w, wb, a, ab, w+, wb+, w+b, a+, ab+, or a+b, and the file did not previously exist, upon successful completion, the fopen() function shall mark for update the st_atime, st_ctime, and st_mtime fields of the file and the st_ctime and st_mtime fields of the parent directory.   If mode is w, wb, w+, wb+, or w+b, and the file did previously exist, upon successful completion, fopen() shall mark for update the st_ctime and st_mtime fields of the file. The fopen() function shall allocate a file descriptor as open() does.   After a successful call to the fopen() function, the orientation of the stream shall be cleared,  the encoding rule shall be cleared, and the associated mbstate_t object shall be set to describe an initial conversion state.   The largest value that can be represented correctly in an object of type off_t shall be established as the offset maximum in the open file description.     RETURN VALUE Upon successful completion, fopen() shall return a pointer to the object controlling the stream. Otherwise, a null pointer shall be returned,  and errno shall be set to indicate the error.     ERRORS The fopen() function shall fail if:   EACCES  Search permission is denied on a component of the path prefix, or the file exists and the permissions specified by mode are denied, or the file does not exist and write permission is denied for the parent directory of the file to be created.  EINTR  A signal was caught during fopen().  EISDIR  The named file is a directory and mode requires write access.  ELOOP  A loop exists in symbolic links encountered during resolution of the path argument.  EMFILE  {OPEN_MAX} file descriptors are currently open in the calling process.  ENAMETOOLONG  The length of the filename argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.   ENFILE  The maximum allowable number of files is currently open in the system.  ENOENT  A component of filename does not name an existing file or filename is an empty string.  ENOSPC  The directory or file system that would contain the new file cannot be expanded, the file does not exist, and the file was to be created.  ENOTDIR  A component of the path prefix is not a directory.  ENXIO  The named file is a character special or block special file, and the device associated with this special file does not exist.  EOVERFLOW  The named file is a regular file and the size of the file cannot be represented correctly in an object of type off_t.  EROFS  The named file resides on a read-only file system and mode requires write access.   The fopen() function may fail if:   EINVAL  The value of the mode argument is not valid.  ELOOP  More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.  EMFILE  {FOPEN_MAX} streams are currently open in the calling process.  EMFILE  {STREAM_MAX} streams are currently open in the calling process.  ENAMETOOLONG  Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.   ENOMEM  Insufficient storage space is available.  ETXTBSY  The file is a pure procedure (shared text) file that is being executed and mode requires write access.   The following sections are informative.     EXAMPLES    Opening a File The following example tries to open the file named file for reading. The fopen() function returns a file pointer that is used in subsequent fgets() and fclose() calls. If the program cannot open the file, it just ignores it.     #include <stdio.h> ... FILE *fp; ... void rgrep(const char *file) { ...     if ((fp = fopen(file, "r")) == NULL)         return; ... }      APPLICATION USAGE None.     RATIONALE None.     FUTURE DIRECTIONS None.     SEE ALSO fclose() , fdopen() , freopen() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h>     COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .  --------------------------------------------------------------------------------

user: user-0
content: 自己先顶一下