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Full Discussion: Count Number Of lines in text files and append values to beginning of file
Top Forums UNIX for Dummies Questions & Answers Count Number Of lines in text files and append values to beginning of file Post 302517858 by alister on Thursday 28th of April 2011 02:36:31 AM
Old 04-28-2011
Quote:
Originally Posted by royalibrahim
INSERTING LINES WITHIN SCRIPTS

If you want to insert a line at the top (or anywhere) of a file within a shell script, use the ed editor.
Code:
string="hello"
ed << \EOF
e any_file
1i
${string}

That code is broken in multiple ways.

First, since the first letter of the heredoc delimiter, EOF, is quoted with a backslash, there will be no substitutions made by the shell within the heredoc. This means that "${string}" will appear literally instead of "hello".

Second, the heredoc delimiter, "EOF", which marks the end of the data is missing.

Third, you need to add a write command, w, to save the changes.

Fourth, before you can use the write command, the text that's inserted needs to be terminated with a lone dot on a line.

It's not all bad news, though. The edit, e, command can be used to load a file into the buffer without invoking ed once per file. If there are a very large number of files, the efficiency of my approach could be improved by only calling ed once and using the for loop to pipe commands into it.

Code:
for f in *; do
        l=$(wc -l < "$f")
        [ $l -lt 400 ] && continue
        printf 'e %s\n0a\nthere are 400 lines in this file and %d bonus lines\n.\nw\n' "$f" $((l-400))
done | ed -s

While the printf could be made more readable with a "%s\n" format string, the clarity of the original heredoc is unmatched by either of
Code:
printf '%s\n' "e $f" 0a "there are 400 lines in this file and $((l-400)) bonus lines" . w

or
Code:
printf '%s\n' \
        "e $f" \
        0a \
        "there are 400 lines in this file and $((l-400)) bonus lines" \
        . \
        w


Bleh. Smilie

Regards,
Alister
Last edited by alister; 04-28-2011 at 04:04 AM..
 

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LEARN ABOUT SUSE

git-sh-setup

GIT-SH-SETUP(1) 						    Git Manual							   GIT-SH-SETUP(1)

NAME

       git-sh-setup - Common git shell script setup code

SYNOPSIS

       . "$(git --exec-path)/git-sh-setup"

DESCRIPTION

       This is not a command the end user would want to run. Ever. This documentation is meant for people who are studying the Porcelain-ish
       scripts and/or are writing new ones.

       The git sh-setup scriptlet is designed to be sourced (using .) by other shell scripts to set up some variables pointing at the normal git
       directories and a few helper shell functions.

       Before sourcing it, your script should set up a few variables; USAGE (and LONG_USAGE, if any) is used to define message given by usage()
       shell function. SUBDIRECTORY_OK can be set if the script can run from a subdirectory of the working tree (some commands do not).

       The scriptlet sets GIT_DIR and GIT_OBJECT_DIRECTORY shell variables, but does not export them to the environment.

FUNCTIONS

       die
	   exit after emitting the supplied error message to the standard error stream.

       usage
	   die with the usage message.

       set_reflog_action
	   set the message that will be recorded to describe the end-user action in the reflog, when the script updates a ref.

       git_editor
	   runs an editor of user's choice (GIT_EDITOR, core.editor, VISUAL or EDITOR) on a given file, but error out if no editor is specified
	   and the terminal is dumb.

       is_bare_repository
	   outputs true or false to the standard output stream to indicate if the repository is a bare repository (i.e. without an associated
	   working tree).

       cd_to_toplevel
	   runs chdir to the toplevel of the working tree.

       require_work_tree
	   checks if the repository is a bare repository, and dies if so. Used by scripts that require working tree (e.g.  checkout).

       get_author_ident_from_commit
	   outputs code for use with eval to set the GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL and GIT_AUTHOR_DATE variables for a given commit.

AUTHOR

       Written by Linus Torvalds <torvalds@osdl.org[1]>

DOCUMENTATION

       Documentation by Junio C Hamano and the git-list <git@vger.kernel.org[2]>.

GIT

       Part of the git(1) suite

NOTES

	1. torvalds@osdl.org
	   mailto:torvalds@osdl.org

	2. git@vger.kernel.org
	   mailto:git@vger.kernel.org

Git 1.7.1							    07/05/2010							   GIT-SH-SETUP(1)
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