Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Editing file
Top Forums Shell Programming and Scripting Editing file Post 302137154 by AnswerGuy on Sunday 23rd of September 2007 03:55:40 AM
Old 09-23-2007
Lightbulb NUL terminate first field of each line?
Rahul,

It sounds like you're trying to NUL terminate the first (whitespace delimited) field (word) of each line in a text file.

That's a very odd request (because the ASCII NUL character is normally used to terminate strings ... but normally NOT embedded in text files ... so many tools that might be trying to read the file line by line would not handle the NUL character gracefully.

It's also possible that your shell or your copy of sed or whatever cannot handle this cleanly. So you might need to use GNU versions of these tools, or a copy of Perl or Python (or compile up a little utility in C, of course).

The most obvious attempt in plain bash would be:

Code:
#!/bin/bash
while IFS="" read line; do 
    set -- $line
    first_word="$1"
    shift
    echo -e "$firstword\000$*"
   done

This is written as a filter so you pipe you file through it. To verify that it's doing what you want you can pipe the output further through a command like cat -A or od -x to be sure it shows the NUL characters where you want them.

That might have some odd artifacts (due to the way that each line is parsed by the set -- command). This following one-liner works in two stages, using sed the first space on each line to a character "177" (octal) --- hex 0x7F, a.k.a. the "DEL" character; and then using the tr command to change that into an ASCII NUL:

Code:
sed -e 's/ /'$(echo -ne '\177')'/' /tmp/foo | tr '\177' '\00'  | cat -A

This assumes that the original file has no ASCII DEL character that you care about preserving ... and the example shows a cat -A just for your convenience. You'd replace that with an appropriate redirection to save your output.

JimD (former Linux Gazette AnswerGuy)
 

10 More Discussions You Might Find Interesting

1. UNIX for Advanced & Expert Users

Editing the end of the file without loading the entire file

hi! I am a newbee. I would really appreciate if you can answer the following question: I have a huge data file, 214MB with several coloumns. I need to delete the very last line of the file. Everything I know takes a lot of time to do it ( because I have to open the file in an editor or run a... (3 Replies)
Discussion started by: Garuda
3 Replies

2. Linux

file editing

I have created a file with vi -x (file name) this is encrypted file when i again open this file it ask me to enter a password before editing it.Can i remove this password but i don't want to delete a file how to do this. Thanks (0 Replies)
Discussion started by: ambavaram
0 Replies

3. Shell Programming and Scripting

Editing a File

Hi all, I have a file with following contents # rad124 # radkus # raddebug # radtrace I could like to remove the # and space present before the key word "rad". Any ways to do this using "subsitution method(:%s/old/new/g)" will be hepful. (1 Reply)
Discussion started by: ramkriz
1 Replies

4. Shell Programming and Scripting

file editing

how to remove duplicate word in a file ? (2 Replies)
Discussion started by: mail2sant
2 Replies

5. Shell Programming and Scripting

Help with file editing while keeping file format intact

Hi, I am having a file which is fix length and comma seperated. And I want to replace values for one column. I am reading file line by line in variable $LINE and then replacing the string. Problem is after changing value and writing new file temp5.txt, formating of original file is getting... (8 Replies)
Discussion started by: Mruda
8 Replies

6. Shell Programming and Scripting

editing line in text file adding number to value in file

I have a text file that has data like: Data "12345#22" Fred ID 12345 Age 45 Wilma Dino Data "123#22" Tarzan ID 123 Age 33 Jane I need to figure out a way of adding 1,000,000 to the specific lines (always same format) in the file, so it becomes: Data "1012345#22" Fred ID... (16 Replies)
Discussion started by: say170
16 Replies

7. Shell Programming and Scripting

Need help in editing a file

I have a file which has 10 million records in it. When am trying to edit the file with vi, the following error occurs: ~ ~ ~ ~ ~ ~ ~ ~ "file1" Value too large for defined data type Is there any way that I can edit this file without using vi? Any help would be really appreciated.... (8 Replies)
Discussion started by: bobby1015
8 Replies

8. UNIX for Dummies Questions & Answers

File editing

Hi All, I've to edit the below file in the Current File: XXX Rows found with null for one or more non-nullable columns in the source table SELECT COUNT(*) FROM ( SELECT 1 as one FROM datum WHERE:wall: datum.ID IS NULL ) a (1 Reply)
Discussion started by: udayakumar
1 Replies

9. Shell Programming and Scripting

File Editing

Never mind!. Thanks (1 Reply)
Discussion started by: smarones
1 Replies

10. Shell Programming and Scripting

Convert vi editing to text editing

Dear Guru's I'm using Putty and want to edit a file. I know we generally use vi editor to do it. As I'm not good in using vi editor, I want to convert the vi into something like text pad. Is there any option in Putty to do the same ? Thanks for your response. Srini (6 Replies)
Discussion started by: thummi9090
6 Replies

LEARN ABOUT X11R4

shift

shift(1)							   User Commands							  shift(1)

NAME

       shift - shell built-in function to traverse either a shell's argument list or a list of field-separated words

SYNOPSIS

   sh
       shift [n]

   csh
       shift [variable]

   ksh
       * shift [n]

DESCRIPTION

   sh
       The positional parameters from $n+1 ... are renamed $1 ... . If n is not given, it is assumed to be 1.

   csh
       The  components of argv, or variable, if supplied, are shifted to the left, discarding the first component. It is an error for the variable
       not to be set or to have a null value.

   ksh
       The positional parameters from $n+1 $n+1 ... are renamed $1 ..., default n is 1. The parameter n can  be  any  arithmetic  expression  that
       evaluates to a non-negative number less than or equal to $#.

       On this man page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

       1.  Variable assignment lists preceding the command remain in effect when the command completes.

       2.  I/O redirections are processed after variable assignments.

       3.  Errors cause a script that contains them to abort.

       4.  Words,  following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a vari-
	   able assignment. This means that tilde substitution is performed after the = sign and word splitting and file name generation  are  not
	   performed.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       csh(1), ksh(1), sh(1), attributes(5)

SunOS 5.10							    15 Apr 1994 							  shift(1)
All times are GMT -4. The time now is 07:27 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy