brand@janus.Berkeley.EDU (Graham Brand) (09/18/90)
I should like some help with a simple problem in Turbo C. I have a C program which I have been running on UNIX with no problem. I am trying to port it to Turbo C 2.0 running on my '386 under MSDOS (V3.3) but am having a strange problem. The program opens files for appending data using the: fopen(fp,filename,"a") construction and writes the data with the usual fprintf(fp,"%s ...%d\n",.....) instruction. The problem that I am having is that the line that is appended in the file is preceeded with a ^Z which makes the data invisible when a type command is issued from MSDOS. I can use vi and edit the file to remove the ^Z but don't want to have to do that every time. Can someone explain what is going on and propose a fix? Thanks in advance, Graham Brand (brand@janus.berkeley.edu)
edgincd2@mentor.cc.purdue.edu (Chris Edgington *Computer Science Major*) (09/18/90)
In article <38742@ucbvax.BERKELEY.EDU>, brand@janus.Berkeley.EDU (Graham Brand) writes: > instruction. The problem that I am having is that the line that is > appended in the file is preceeded with a ^Z which makes the data > invisible when a type command is issued from MSDOS. I can use vi and Is the ^Z leftover from the original dos file or is it the first character of the append data?? If it is leftover from the original file, you could you fsetpos to set the position for writing as eof(original)-1, then it would erase the ^Z Chris
toma@tekgvs.LABS.TEK.COM (Tom Almy) (09/19/90)
In article <38742@ucbvax.BERKELEY.EDU> brand@janus.Berkeley.EDU writes: >I should like some help with a simple problem in Turbo C. I have a >C program which I have been running on UNIX with no problem. I am >trying to port it to Turbo C 2.0 running on my '386 under MSDOS (V3.3) >but am having a strange problem. The program opens files for appending >data using the: I'm sure you mean fp=fopen(filename,"a") > fopen(fp,filename,"a") >construction and writes the data with the usual > fprintf(fp,"%s ...%d\n",.....) >instruction. The problem that I am having is that the line that is >appended in the file is preceeded with a ^Z which makes the data >invisible when a type command is issued from MSDOS. The file undoubtedly had the ^Z character at the end when you started. You can't delete it when opening in "a" mode because this mode forces all writes to occur at the end of file. You will need to do something like this: if (fp = fopen(filename,"r+") { /* file exists */ fseek(fp,-1L,SEEK_END); /* check last character */ if (fgetc(fp) == 26) /* last character is a control-Z, delete it */ fseek(fp,-1L,SEEK_END); } else { /* file does not already exist */ if ((fp = fopen(filename,"w")) == NULL) { /* Error code for unable to create file */ } } Tom Almy toma@tekgvs.labs.tek.com Standard Disclaimers Apply
brand@janus.Berkeley.EDU (Graham Brand) (09/27/90)
Dear All,
Thanks to the 6 or so of you who replied. No one respondent in
particular was completely correct; the solution turned out to be a
combination of things. Most people mentioned the history of CP/M and ^Z
and so suggested using the fseek(fp,-1L,SEEK_END) approach. A couple
suggested using the "b" access_mode option as in
fp=fopen("filename","rb+"). The solution that worked uses both of these.
I must admit that I am not too sure why, but having spent more time on
this simple problem than I had intended, I shan't worry about it too
much.
Before I lay the problem to rest, though, there is one peculiar
aspect that I have not resolved. It is the fact that, before I added the
fixes to the program, even if I ensured that the file did **NOT** have
a ^Z eof termination when I started, my program would prepend a ^Z to
any line of text that was added to the end of the file. The only file
operations that were done in the program were fopen() and fprintf()?
Where was the ^Z coming from and which of the changes, fseek(.,-1L,.) or
fopen(.,"b"), cured it?
Thanks for all your help,
-Grahammgphl@msa3b.UUCP (Michael Phillips) (09/29/90)
brand@janus.Berkeley.EDU (Graham Brand) writes: >... >any line of text that was added to the end of the file. The only file >operations that were done in the program were fopen() and fprintf()? >Where was the ^Z coming from and which of the changes, fseek(.,-1L,.) or >fopen(.,"b"), cured it? >Thanks for all your help, >-Graham Graham, Absolutely, positively, it was the fopen(.,"b") that cured your ^Z problem. Since ^Z is the "end-of-file" marker for _TEXT_ files, anytime a file is opened as _text_ ("t", the usual default), and the file is updated in some way, it should have a ^Z appended to the end. Now I think that the ^Z is basically useless, but it is the way DOS defines things so I live with it. Michael *-----------------------------------------------------------------------* D&B Software Atlnata, GA - "Constants aren't and Variables don't"