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Full Discussion: How to read a file starting at certain line number?
Top Forums Shell Programming and Scripting How to read a file starting at certain line number? Post 302950856 by rbatte1 on Wednesday 29th of July 2015 12:01:11 PM
Old 07-29-2015
It depends what you mean by "...read a file line by line from a certain line number."

The command tail with appropriate options might give you what you want. Can you elaborate on the requirement? Perhaps something like:-
Code:
tail +$lineNumber file

You can pass this into a loop line this:-
Code:
tail +$lineNumber file | while read line
do
    ..... # Whatever you need
done

You can make it more elaborate if you have multiple fields and/or field separators, so if it was colon separated : and you want to read five fields, you can:-
Code:
tail +$lineNumber file | while IFS=: read f1 f2 f3 f4 f5 
do
    ..... # Whatever you need
done



However, if you are just after a single line, you could use:-
Code:
sed -n${lineNumber}p file

Beware that this will read a single line and is therefore very IO intensive if you want to read multiple time from a file working down it.



I hope that these structures help. Can you explain a little more about the requirements?

Robin
 

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LEARN ABOUT HPUX

dteditorgotoline

DtEditorGoToLine(library call)											    DtEditorGoToLine(library call)

NAME

       DtEditorGoToLine -- move the insert cursor for a DtEditor widget to a specified line

SYNOPSIS

       #include <Dt/Editor.h>
       void DtEditorGoToLine(
       Widget widget,
       int lineNumber);

DESCRIPTION

       The  DtEditorGoToLine  function	moves  the  insert cursor for the DtEditor widget to the beginning of the line specified by the lineNumber
       argument.  The cursor can be moved to the last line by specifying DtEDITOR_LAST_LINE as the line number.  If the line is not currently  on-
       screen, the contents for the DtEditor widget are scrolled to display the new insertion position.

       The lineNumber argument is the number of the line in the file, counting from 1.	If the lineNumber argument is less than 1, the insert cur-
       sor is placed at the beginning of the first line.  If the argument is greater than the total number of lines, the cursor is placed  at  the
       last line of text.

       The  insert  cursor can be moved to a specific character position with DtEditorSetInsertionPosition(3). The DtNtopCharacter resource can be
       used to control which line is displayed at the top of the DtEditor widget.

       The widget argument specifies the DtEditor widget ID.

       The lineNumber argument specifies the line number within the DtEditor widget.

       For a complete definition of the DtEditor widget and its associated resources, see DtEditor(3).

RETURN VALUE

       The DtEditorGoToLine function returns no value.

SEE ALSO

       Dt/Editor.h - DtEditor(5), DtEditor(3), DtEditorSetInsertionPosition(3).

														    DtEditorGoToLine(library call)
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