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Top Forums Shell Programming and Scripting How to read n number of lines from a file Post 302361004 by jp2542a on Monday 12th of October 2009 01:02:14 AM
Old 10-12-2009
Code:
#!/bin/bash
echo "Enter file name"
read file
echo "Enter the number"
read n
awk -v count=$n '{k = $1; getline; for (j=1; j<cunt; j++) {if ( $1 > k ) k = $1; getline; } print k}' $file

 

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GETDELIM(3)						   BSD Library Functions Manual 					       GETDELIM(3)

NAME
getdelim, getline -- read a delimited record from a stream LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <stdio.h> ssize_t getdelim(char ** restrict lineptr, size_t * restrict n, int delimiter, FILE * restrict stream); ssize_t getline(char ** restrict lineptr, size_t * restrict n, FILE * restrict stream); DESCRIPTION
The getdelim() function reads from the stream until it encounters a character matching delimiter, storing the input in *lineptr. The buffer is NUL-terminated and includes the delimiter. The delimiter character must be representable as an unsigned char. If *n is non-zero, then *lineptr must be pre-allocated to at least *n bytes. The buffer should be allocated dynamically; it must be possible to free(3) *lineptr. getdelim() ensures that *lineptr is large enough to hold the input, updating *n to reflect the new size. The getline() function is equivalent to getdelim() with delimiter set to the newline character. RETURN VALUES
The getdelim() and getline() functions return the number of characters read, including the delimiter. If no characters were read and the stream is at end-of-file, the functions return -1. If an error occurs, the functions return -1 and the global variable errno is set to indi- cate the error. The functions do not distinguish between end-of-file and error, and callers must use feof(3) and ferror(3) to determine which occurred. EXAMPLES
The following code fragment reads lines from a file and writes them to standard output. char *line = NULL; size_t linesize = 0; ssize_t linelen; while ((linelen = getline(&line, &linesize, fp)) != -1) fwrite(line, linelen, 1, stdout); if (ferror(fp)) perror("getline"); ERRORS
[EINVAL] lineptr or n is a NULL pointer. [EOVERFLOW] More than SSIZE_MAX characters were read without encountering the delimiter. The getdelim() and getline() functions may also fail and set errno for any of the errors specified in the routines fflush(3), malloc(3), read(2), stat(2), or realloc(3). SEE ALSO
ferror(3), fgets(3), fopen(3) STANDARDS
The getdelim() and getline() functions conform to IEEE Std 1003.1-2008 (``POSIX.1''). BSD
June 30, 2010 BSD
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