file write
in [Learn C or C++]
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From: raaki on 25 Jun 2008 03:25 Hello group members, i am a newbie and trying to write array values to a file. array values are dynamic so i need to create file first and later append the values here is the code i tried... the file is created but it is empty can any one help.... void filewrite (unsigned int *sad, unsigned char *path) { unsigned int i; unsigned int *dat; unsigned int *write_tmp; int op_return; unsigned int tmp; dat = &sad[0]; write_tmp = malloc (sizeof (unsigned int)); op_return = open (path, O_CREAT | O_APPEND, S_IRWXU | S_IRWXG); if (op_return < 0) { printf ("Error in opening file %s\n", path); //exit(0); } for (i = 0; i < 980; i++) { tmp = (unsigned int) dat[0]; write_tmp = &tmp; write (op_return ,write_tmp, 2); dat++; } close (op_return); } main(){ constant char* path = "./file.txt"; .... ... filewrite (sad,path); ... ... } there is one warning In function `filewrite': warning: passing arg 2 of `write' from incompatible pointer type
From: Jerry Coffin on 25 Jun 2008 09:43 In article <adc51911-fdcb-4735-8ba5-360ad83c8141@ 79g2000hsk.googlegroups.com>, hemanth004(a)gmail.com says... > Hello group members, > > i am a newbie and trying to write array values to a file. > > array values are dynamic > > so i need to create file first and later append the values [ ... ] At least for now you should probably avoid using open() and write() directly. You haven't said whether you're using C or C++ though. If you're using C++, I'd advise using an std::ofstream. For that matter, I'd advise that you avoid using an array directly, and use an std::vector instead. An std::vector automatically handles the dynamic allocation for you, and keeps track of its own size. If you're using C, you probably want to use a FILE * instead. If I'm understanding the intent of your code correctly, a rough equivalent using an ofstream would look something like: void filewrite(unsigned int *sad, char const *path) { std::ofstream outfile(path, std::ios::binary); outfile.write((char *)sad, 980*sizeof(unsigned int)); } Using a FILE *, this would look only slightly different: void filewrite(unsigned int *sad, char const *path) { FILE *outfile = fopen(path, "wb"); fwrite(sad, sizeof(unsigned int), 980, outfile); } Even if you insist on continuing to use open() and write(), you probably want to do it differently -- specifically, you want to write the entire array as a single chunk instead of writing each element individually: void filewrite(unsigned int *sad, char const *path) { int file_handle = open(path, O_CREAT); write(file_handle, sad, 980*sizeof(unsigned int)); } In all of these, I've left the assumption that sad points to an array of 980 unsigned ints. You almost never want to make an assumption like that in real code; likewise, you almost never want to hard-code a value like '980' into your code either. -- Later, Jerry. The universe is a figment of its own imagination.
From: raaki on 25 Jun 2008 11:55 Hi Jerry, thanks for ur suggestions.i forget to menction that i am using C and in real script 980 is replaced by variable. i am not using stdio.h to use FILE option. we use our own written lib(headers) where write is defined as int write(int fdesc,char* buf,unsigned long int nbyte) // usava unsigned int { asm("break 0x131"); asm("nop"); } in the header file . even after ur suggestions i still have the same problem tried options are void filewrite(unsigned int *sad, char const *path) { int file_handle = open(path, O_CREAT|O_APPEND, S_IRWXU| S_IRWXG); write(file_handle, sad, 1); } other method ... void filewrite (unsigned int *sad, unsigned char *path) { unsigned int i; unsigned int *dat; unsigned int *write_tmp; int op_return; unsigned int tmp; dat = &sad[0]; write_tmp = malloc(sizeof (char)); op_return = open (path,O_CREAT|O_APPEND, S_IRWXU|S_IRWXG); if (op_return < 0) { printf ("Error in opening file %s\n", path); exit(0); } else { tmp = (char)dat[0]; write_tmp=&tmp; write (op_return , write_tmp , 1); dat++; } close (op_return); } i still get the same warning as i have stated bfore and the file is empty. any other ideas... thks, raaki
From: Jerry Coffin on 25 Jun 2008 12:02 In article <8021a285-b73b-49f2-b3f4-f37f0c7871a6 @m44g2000hsc.googlegroups.com>, hemanth004(a)gmail.com says... > Hi Jerry, > > thanks for ur suggestions.i forget to menction that i am using C and > in real script 980 is replaced by variable. > > i am not using stdio.h to use FILE option. > > we use our own written lib(headers) where write is defined as [ ... ] > i still get the same warning as i have stated bfore and the file is > empty. > > any other ideas... It sounds a great deal as if the 'write' function you've defined simply doesn't work. -- Later, Jerry. The universe is a figment of its own imagination.
From: raaki on 25 Jun 2008 12:28
On Jun 25, 6:02 pm, Jerry Coffin <jcof...(a)taeus.com> wrote: > In article <8021a285-b73b-49f2-b3f4-f37f0c7871a6 > @m44g2000hsc.googlegroups.com>, hemanth...(a)gmail.com says... > > > Hi Jerry, > > > thanks for ur suggestions.i forget to menction that i am using C and > > in real script 980 is replaced by variable. > > > i am not using stdio.h to use FILE option. > > > we use our own written lib(headers) where write is defined as > > [ ... ] > > > i still get the same warning as i have stated bfore and the file is > > empty. > > > any other ideas... > > It sounds a great deal as if the 'write' function you've defined simply > doesn't work. > > -- > Later, > Jerry. > > The universe is a figment of its own imagination. my intension is to show you those are the parameters needed for write func,but exact header description i couldnt find what about the procedures tried,is there any mistake? thks , raaki |