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Full Discussion: Bash script to find comments in file
Top Forums Shell Programming and Scripting Bash script to find comments in file Post 302925893 by Don Cragun on Thursday 20th of November 2014 02:35:18 AM
Old 11-20-2014
For the purposes of this exercise, how do you define "comment"?

A basic outline of what you want is something like:
Code:
#!/bin/bash
n=1
while read -r line
do      if [ comment_present ]
        then    printf '%d\t%s\n' $n "$line"
        fi
        n=$((n + 1))
done < file

If you assume that any line containing an octothorpe (#) has a comment, comment_present could be:
Code:
"$line" != "${line#*#}"

but, of course, that will treat quoted and backslash escaped octothorpes as comments when bash would not.

Writing a full parser to find C or shell or some other language's comments accurately in bash is a non-trivial challenge.
Last edited by Don Cragun; 11-20-2014 at 03:38 AM.. Reason: Print line number and line; not just line number.
This User Gave Thanks to Don Cragun For This Post:
ksmarine1980
 

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LEARN ABOUT BSD

learn

LEARN(1)						      General Commands Manual							  LEARN(1)

NAME

       learn - computer aided instruction about UNIX

SYNOPSIS

       learn [ -directory ] [ subject [ lesson ] ]

DESCRIPTION

       Learn gives Computer Aided Instruction courses and practice in the use of UNIX, the C Shell, and the Berkeley text editors.  To get started
       simply type learn.  If you had used learn before and left your last session without completing a subject, the program will use  information
       in  $HOME/.learnrc  to start you up in the same place you left off.  Your first time through, learn will ask questions to find out what you
       want to do.  Some questions may be bypassed by naming a subject, and more yet by naming a lesson.  You may enter the  lesson  as  a  number
       that  learn  gave you in a previous session.  If you do not know the lesson number, you may enter the lesson as a word, and learn will look
       for the first lesson containing it.  If the lesson is `-', learn prompts for each lesson; this is useful for debugging.

       The subject's presently handled are

	    files
	    editor
	    vi
	    morefiles
	    macros
	    eqn
	    C

       There are a few special commands.  The command `bye' terminates a learn session and `where' tells you  of  your	progress,  with  `where m'
       telling	you  more.  The command `again' re-displays the text of the lesson and `again lesson' lets you review lesson.  There is no way for
       learn to tell you the answers it expects in English, however, the command `hint' prints the last part of the lesson script used to evaluate
       a  response, while `hint m' prints the whole lesson script.  This is useful for debugging lessons and might possibly give you an idea about
       what it expects.

       The -directory option allows one to exercise a script in a nonstandard place.

FILES

       /usr/share/learn    subtree for all dependent directories and files
       /usr/tmp/pl*   playpen directories
       $HOME/.learnrc startup information

SEE ALSO

       csh(1), ex(1)
       B. W. Kernighan and M. E. Lesk, LEARN - Computer-Aided Instruction on UNIX

BUGS

       The main strength of learn, that it asks the student to use the real UNIX, also makes possible baffling mistakes.   It  is  helpful,  espe-
       cially for nonprogrammers, to have a UNIX initiate near at hand during the first sessions.

       Occasionally lessons are incorrect, sometimes because the local version of a command operates in a non-standard way.  Occasionally a lesson
       script does not recognize all the different correct responses, in which case the `hint' command may be useful.  Such lessons may be skipped
       with the `skip' command, but it takes some sophistication to recognize the situation.

       To find a lesson given as a word, learn does a simple fgrep(1) through the lessons.  It is unclear whether this sort of subject indexing is
       better than none.

       Spawning a new shell is required for each of many user and internal functions.

       The `vi' lessons are provided separately from the others.  To use them see your system administrator.

7th Edition							 October 22, 1996							  LEARN(1)
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