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Top Forums Shell Programming and Scripting for loop iteration and shell programming startup Post 302589982 by methyl on Friday 13th of January 2012 09:33:04 AM
Old 01-13-2012
Java

Quote:
question :how can i iterate to next item in for loop with the loop
e.g

for i in `cat abc.txt`
do
echo $i // this will display first line
i=$i+1; // this doesnt work for me.
echo $i; //this will display secound line
done
If we are working with lines, we do not want to expand the entire file "abc.txt" on the "for" line and then read it word by word.
We need to read each line one-by one with a method which preserves the record construct.
Code:
cat abc.txt | while read line
do
          echo "${line}"          # Display line
done

To make the extra read in the while loop:
Code:
cat abc.txt | while read line
do
          echo "${line}"          # Display first line and every odd-numbered line
          read line                  # Read even numbered lines
          echo "${line}"           # Display 2nd line and every even-numbered line
done


Don't understand your second question. Not clear which file is which or what the process is.
This User Gave Thanks to methyl For This Post:
 

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FGETS(3)								 1								  FGETS(3)

fgets - Gets line from file pointer

SYNOPSIS
string fgets (resource $handle, [int $length]) DESCRIPTION
Gets a line from file pointer. PARAMETERS
o $handle -The file pointer must be valid, and must point to a file successfully opened by fopen(3) or fsockopen(3) (and not yet closed by fclose(3)). o $length - Reading ends when $length - 1 bytes have been read, or a newline (which is included in the return value), or an EOF (whichever comes first). If no length is specified, it will keep reading from the stream until it reaches the end of the line. Note Until PHP 4.3.0, omitting it would assume 1024 as the line length. If the majority of the lines in the file are all larger than 8KB, it is more resource efficient for your script to specify the maximum line length. RETURN VALUES
Returns a string of up to $length - 1 bytes read from the file pointed to by $handle. If there is no more data to read in the file pointer, then FALSE is returned. If an error occurs, FALSE is returned. CHANGELOG
+--------+-----------------------------+ |Version | | | | | | | Description | | | | +--------+-----------------------------+ | 4.3.0 | | | | | | | fgets(3) is now binary safe | | | | +--------+-----------------------------+ EXAMPLES
Example #1 Reading a file line by line <?php $handle = @fopen("/tmp/inputfile.txt", "r"); if ($handle) { while (($buffer = fgets($handle, 4096)) !== false) { echo $buffer; } if (!feof($handle)) { echo "Error: unexpected fgets() fail "; } fclose($handle); } ?> NOTES
Note If PHP is not properly recognizing the line endings when reading files either on or created by a Macintosh computer, enabling the auto_detect_line_endings run-time configuration option may help resolve the problem. Note People used to the 'C' semantics of fgets(3) should note the difference in how EOF is returned. SEE ALSO
fgetss(3), fread(3), fgetc(3), stream_get_line(3), fopen(3), popen(3), fsockopen(3), stream_set_timeout(3). PHP Documentation Group FGETS(3)
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