I recently got to know that, if a hash mark (#) to begin a shell comment is not placed at the beginning of a line, then the hash mark must be preceded by a horizontal whitespace. (The # mark is also called a "pound sign" in the United States, and a "number sign" as a Unicode name.)
I have never seen any Unix guide documents explicitly state the need for a space before a hash mark (#) to begin a comment. C++ allows comment-leading double slashes (//) to immediately follow another token without any spaces preceding the double slashes. So, I thought that BASH would not require any spaces before a hash mark (#) that begins a comment.
I recently read carefully a man page of bash, which writes, "a word beginning with # causes that word and all remaining characters on that line to be ignored." The phrase "a word beginning with #" obscurely implies that a space is required before # if the comment-leading # is not placed at the beginning of a line.
Now, let me go back to my initial problem. I need to compare two copies of a bash script. One copy is full of detailed comments. The other copy has few or no comments. The two copies differ also in spacing. In terms of command statements that affect execution, the two copies are almost identical. So, I would like to remove comments before comparing the two copies. The following script now gives me most of what I wanted. I named the script "rmcomment.sh".
It may be a no-brainer, but the answer is escaping me right now:
I'm trying to write a little script to remove all comments from .c source... I was thinking sed, but I'm not a very strong regexp user (e.g. I suck with sed).
I tried dumping the file into:
sed -e 's/\/\* * \*\///g'
and several... (1 Reply)
#! /bin/sed -nf
# Remove C and C++ comments, by Brian Hiles (brian_hiles@rocketmail.com)
# Sped up (and bugfixed to some extent) by Paolo Bonzini (bonzini@gnu.org)
# Works its way through the line, copying to hold space the text up to the
# first special character (/, ", '). The original... (1 Reply)
Suppose i have a file like this:
#bla bla
#bla bla bla bla bla
Bla
BLA
BLA BLA #bla bla
....
....
how can i remove all comments from every line,even if they are behind commands or strngs that are not comments?
any idea how i could do that using awk? (2 Replies)
I must write a script to change all C++ like comments:
// this is a comment
to this one
/* this is a comment */
How to do it by sed? With file:
#include <cstdio>
using namespace std; //one
// two
int main() {
printf("Example"); // three
}//four
the result should be: (2 Replies)
Hi,
I am using BASH. How can I remove any lines in a text file that are either blank or begin with a # (ie. comments)? Thanks in advance.
Mike (3 Replies)
I need to use sed to remove comments from files. I am using this, but it only works on comments that start at the beginning of the line.
sed /^"\/\/"/d
In most of the files I have comments like this:
code // Comments
or
tab // Comments (5 Replies)
I have tried a lot, Need your help guys.
SAS Program:
data one ; /* Data step */
Input name $; /*Dec variables*/
I want to remove the commented part(/* Data step */) alone. I have tried using sed command but it is deleting the entire line itself. i need unix command to separate this and... (1 Reply)
As I stated in a previous thread - I'm a newbie to Unix/Linux and programming. I'm trying to learn the basics on my own using a couple books and the exercises provided inside.
I've reached an exercise that has me stumped. I need to write a bash script that will will read in a file and print the... (11 Replies)
Hi , We need to remove comment like pattern from a code text. The possible comment expressions are as follows.
Input
BizComment : Special/*@
Name:bzt_53_3aea640a_51783afa_5d64_0
BizHidden:true
@*/
/* lookup Disease
Category Therapuetic Class */
a=b;... (6 Replies)
Discussion started by: VikashKumar
6 Replies
LEARN ABOUT OSF1
unifdef
unifdef(1) General Commands Manual unifdef(1)NAME
unifdef - Removes #ifdefed lines
SYNOPSIS
unifdef [-tlc] [-Dsymbol] [-idsymbol] [-iusymbol] [file] [-Usymbol]
The unifdef command partially simulates the behavior of the C preprocessor in processing #ifdef conditionals.
OPTIONS
Complements the action of unifdef; retains lines that would normally be removed and removes lines that would normally be retained. Speci-
fies symbol as a defined #ifdef symbol. Specifies defined lines inside certain #ifdefs to be ignored but copied out. Specifies undefined
lines inside certain #ifdefs to be ignored and not copied out. Replaces removed lines with blank lines instead of deleting them. Pro-
cesses plain text (rather than C code) input. The unifdef command does not try to recognize comments, single quotes, and double quotes.
Specifies symbol as an undefined #ifdef symbol.
DESCRIPTION
The unifdef command recognizes nested #ifdefs, comments, single and double quotes of C syntax so that it can function correctly, but does
not include files or interpret macros. The unifdef command recognizes, but does not remove comments.
The unifdef command takes its input from stdin if no file argument is given, and copies its output to stdout.
You specify the symbols you want defined with -Dsymbol or undefined with -Usymbol and the lines inside those #ifdefs are copied to the out-
put or removed, as appropriate. The #ifdef, #ifndef, #else, #elif, and endif lines associated with symbol are also removed. The #ifdefs
involving unspecified symbols are untouched and copied out along with their associated #ifdef, #else, elif, and #endif lines. If the same
symbol appears in more than one argument, only the first occurrence is significant. For instance, if an #ifdef X occurs nested inside
another #ifdef X, the inside #ifdef is considered an unrecognized symbol.
If you use #ifdefs to delimit non-C lines, such as comments or unfinished code, it is necessary to specify which symbols are to be used for
that purpose. Otherwise, the unifdef command tries to parse for quotes and comments in those #ifdef lines.
Keywords
The following keywords can be used with the unifdef command:
ifdef ifndef else endif elif
The unifdef command uses the elif keyword as follows. (Note that "Understood" means unifdef knows how to convert elif to if.) Understood
Not understood Not understood
For example:
# ifdef X x # elif defined (Y) y # elif defined (A) || defined (B) a # else default # endif
The following list shows the results of using the elif keyword with variables:
-DX x
-UX # if defined (Y) y # elif defined (A) || defined (B) a # else default # endif -UX -DY y
-UY -UX # if defined (Y) y # elif defined (A) || defined (B) a # else default # endif
-UY -UX -DA # if defined (Y) y # elif defined (A) || defined (B) a # else default # endif
NOTES
The unifdef command cannot process cpp constructs such as:
#if defined(X) || defined(Y)
DIAGNOSTICS
The unifdef command can fail for several reasons: a premature end of file, or an inappropriate else, elif, or endif.
EXIT STATUS
Exit status is 0 if output is an exact copy of input, 1 if not, 2 if the unifdef command fails.
EXAMPLES
The following command line causes the unifdef command to read the file original.c and remove the #ifdef A lines. It then removes every-
thing following an #elif/#else associated with the #ifdef A down to the #endif: unifdef -DA original.c > modified.c The following command
line causes the unifdef command to read the file original.c, and remove the #ifdef A down to either its associated #elif/#else, or its
associated #endif: unifdef -UA original.c > modified.c
In the case of the #elif, the #elif is replaced with #if. In the case of #else, the #else is deleted along with its associated
#endif.
SEE ALSO
Commands: diff(1)unifdef(1)