Sponsored Content
Top Forums Programming how to move file pointer to a particular line in c Post 302178585 by user_prady on Wednesday 26th of March 2008 12:52:35 AM
Old 03-26-2008
Quote:
Originally Posted by ramkrix
Hi,

I beleive you can do it with fseek itself by mentioning the bytes. See our terminal is 23*79, I mean to say 23 rows and 79 columns.

Say, if we have each coulmn occupies 1 character exactly, it means 1 byte. Therefore, a line can have 79 bytes of data in it. Then to move the nth line, you can use this formula
byte position=(((n-1)*number of bytes per line)+1).
I derived this formula, hope it will work.

Put this byte position in your fseek() function.

Please find the number of characters or bytes occpied by each column in a line of terminal. ere I assumed each column occupies 1 charcter and derived the formula.

please revert me back with the solution resulted.

regards,
Ramkrix
Thanks for the reply..
But how to know number of bytes per line . Its changing per line in my case.

I tried something like follow but still in half way.
Code:
int i ;
char data[80];
long cur_pos[200];
while( feof(fh) == 0){
            cur_pos[i++] = ftell(fh);
 printf( "cur_cursor = %ld i= %d\n", cur_pos[i],i);
            fgets(data, 80, fh);
     }

output
Code:
cur_cursor = 1128098488 i= 1
cur_cursor = -30932 i= 2
cur_cursor = -30960 i= 3
cur_cursor = 1127283141 i= 4

In the above case it displays me something starnage output but when i change the above code to following

Code:
char data[80];
long cur_pos;
while( feof(fh) == 0){
            cur_pos = ftell(fh);
 printf( "cur_cursor = %ld \n", cur_pos);
            fgets(data, 80, fh);
    }

I am getting what I supposed to get.
output:
Code:
cur_cursor = 0
cur_cursor = 20
cur_cursor = 39
cur_cursor = 59
cur_cursor = 81
cur_cursor = 102
cur_cursor = 121

But still I cant find out my sol..
Thanks in advance..

Last edited by user_prady; 03-26-2008 at 02:02 AM..
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Perl how to move pointer to previous line in a txt file?

I have a text file that has blocks of text. Each block starts with ### and ends with End_###. I wrote a perl script to search a string from line 2 (ignore any line starts with ###) of each block if matched, need to print that whole block. According to the input file in below, it will print... (5 Replies)
Discussion started by: tqlam
5 Replies

2. Shell Programming and Scripting

how to move the line after a certain pattern in the file

Hi, I have a file called /bb/bin/rstrt. I need to move the line/entry "ccpm_load_shared_memory" after the entry "initcorp". The problem is that there are several entries for "initcorp" in this file and I need the entry to be moved only after the first instance of "initcorp" Is there a way... (5 Replies)
Discussion started by: aoussenko
5 Replies

3. Shell Programming and Scripting

Script to move the first line of a file to the end

I'm rather new to scripting, and despite my attempts at finding/writing a script to do what I need, I have not yet been successful. I have a file named "list.txt" of arbitrary length with contents in the following format: /home/user/Music/file1.mp3 /home/user/Music/file2.mp3... (21 Replies)
Discussion started by: Altay_H
21 Replies

4. Programming

pass a pointer-to-pointer, or return a pointer?

If one wants to get a start address of a array or a string or a block of memory via a function, there are at least two methods to achieve it: (1) one is to pass a pointer-to-pointer parameter, like: int my_malloc(int size, char **pmem) { *pmem=(char *)malloc(size); if(*pmem==NULL)... (11 Replies)
Discussion started by: aaronwong
11 Replies

5. Shell Programming and Scripting

Move a line to end of file

Can somebody help me with a script .... Read a file /etc/inittab find the string starting with rcml and move it entirely towards the end of file. rcml:2:once:/usr/sni/aix52/rc.ml > /dev/console 2>&1 I basically want to change the startup sequence. (2 Replies)
Discussion started by: imanuk2007
2 Replies

6. Shell Programming and Scripting

awk - if field is empty, move line to new file

I have a script with this statement: /usr/xpg4/bin/awk -F"" 'NR==FNR{s=$2;next}{printf "%s\"%s\"\n", $0, s}' LOOKUP.TXT finallistnew.txt >test.txt I want to include logic or an additional step that says if there is no data in field 3, move the whole line out of test.txt into an additional... (9 Replies)
Discussion started by: scriptr2be
9 Replies

7. Shell Programming and Scripting

move contents from one file to another based on line number or content

I want a script that will move everything beyond a certain line number or beyond a certain content word into another file. For example, if file A has this: first line second line third line forth line fifth line sixth line I want to run a script that will move everything beyond the third... (4 Replies)
Discussion started by: robp2175
4 Replies

8. Shell Programming and Scripting

Move a text to next line in a file

Hi , I need your help for the below issue. I have a file which has data as below An error came (/u01/app/12.csv) pkg1.func1: detail s 1111-->pkg1.func1: detail s 2222--> Now pkg1.func1: .... --> can come multiple times in the second line. I need to arrange the data in the below... (9 Replies)
Discussion started by: bhaski2012
9 Replies

9. Shell Programming and Scripting

Move a line to top of the file

Hi, I have a following file and it has only one occurrence of line that says "Output view:". It could be in middle somewhere ( i don't know the exact location ). I want to move it as the first line of the file. Input AAA BBBB CCCC Output view: XXXX YYYY ZZZZ Output should be: Output... (13 Replies)
Discussion started by: jakSun8
13 Replies

10. Solaris

Solaris 5.10 "Move Pointer" stuck

Hey there, I joined this forum just now cause I need help with an old SUN machine at work. I work on a helpdesk and we use a SOLARIS 5.10 OS. Every once in a while we will try to move one of our windows out of the way to make room on the desktop, and sometimes the mouse doesn't release what we... (7 Replies)
Discussion started by: TRex_2005
7 Replies
FSEEK(3)						     Linux Programmer's Manual							  FSEEK(3)

NAME
fgetpos, fseek, fsetpos, ftell, rewind - reposition a stream SYNOPSIS
#include <stdio.h> int fseek(FILE *stream, long offset, int whence); long ftell(FILE *stream); void rewind(FILE *stream); int fgetpos(FILE *stream, fpos_t *pos); int fsetpos(FILE *stream, fpos_t *pos); DESCRIPTION
The fseek function sets the file position indicator for the stream pointed to by stream. The new position, measured in bytes, is obtained by adding offset bytes to the position specified by whence. If whence is set to SEEK_SET, SEEK_CUR, or SEEK_END, the offset is relative to the start of the file, the current position indicator, or end-of-file, respectively. A successful call to the fseek function clears the end-of-file indicator for the stream and undoes any effects of the ungetc(3) function on the same stream. The ftell function obtains the current value of the file position indicator for the stream pointed to by stream. The rewind function sets the file position indicator for the stream pointed to by stream to the beginning of the file. It is equivalent to: (void)fseek(stream, 0L, SEEK_SET) except that the error indicator for the stream is also cleared (see clearerr(3)). The fgetpos and fsetpos functions are alternate interfaces equivalent to ftell and fseek (with whence set to SEEK_SET), setting and storing the current value of the file offset into or from the object referenced by pos. On some non-UNIX systems an fpos_t object may be a complex object and these routines may be the only way to portably reposition a text stream. RETURN VALUE
The rewind function returns no value. Upon successful completion, fgetpos, fseek, fsetpos return 0, and ftell returns the current offset. Otherwise, -1 is returned and the global variable errno is set to indicate the error. ERRORS
EBADF The stream specified is not a seekable stream. EINVAL The whence argument to fseek was not SEEK_SET, SEEK_END, or SEEK_CUR. The function fgetpos, fseek, fsetpos, and ftell may also fail and set errno for any of the errors specified for the routines fflush(3), fstat(2), lseek(2), and malloc(3). CONFORMING TO
The fgetpos, fsetpos, fseek, ftell, and rewind functions conform to ANSI X3.159-1989 (``ANSI C''). SEE ALSO
lseek(2), fseeko(3) BSD MANPAGE
1993-11-29 FSEEK(3)
All times are GMT -4. The time now is 04:40 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy