File Bundles

August 14, 2015

It is sometimes convenient to package a group of files into a bundle, for transmission to a different computer or for archiving. Nowadays the most likely method involves tar and gzip, but in the past a “shell archive” was frequently used; the files, which are assumed to include only printable ascii characters, are collected into a single program file that can be executed to self-extract the included files.

Your task is to write a program that creates file bundles. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.

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2 Responses to “File Bundles”

  1. Rutger said

    Python is the new shell..

    This creates a self extracting py file:

    code = """\
    def write_file((filename, lines)):
    	out = open(filename, 'w')
    	for line in lines:
    		out.write(line)
    	out.close()
    
    files = []
    """
    
    def make_self_extracting_py(files):
    	out = open('self_extracter.py', 'w')
    	out.write(code)
    	for i,filename in enumerate(files):
    		content = open(filename).readlines()
    		out.write("files.append(('{0}', {1}))".format(filename, content))
    		out.write("\n")
    	out.write("map(write_file, files)")
    	out.close()
    
    make_self_extracting_py(['text1.TXT', 'text2.TXT'])
    

    content of text1.TXT:
    hello world
    bye world

    content of text2.TXT:
    test with ‘qoutes’ and all other “stuf” should get ‘””” “””””IUYE754^!^#!%$#!%#*^ escaped..

    result of above script is:

    def write_file((filename, lines)):
    	out = open(filename, 'w')
    	for line in lines:
    		out.write(line)
    	out.close()
    
    files = []
    files.append(('text1.TXT', ['hello world\n', 'bye world']))
    files.append(('text2.TXT', ['test with \'qoutes\' and all other "stuf" should get \'"\'\'\'\' """""IUYE754^!^#!%$#!%#*^   escaped..']))
    map(write_file, files)
    

    This can be run, result is original text files content again.

  2. mcmillhj said
    #!/usr/bin/env perl
    
    use strict;
    use warnings;
    
    sub make_shell_archive {
       my ($filenames) = @_;
    
       open my $outfile_fh, '>', 'extract_files.sh'
          or die "Unable to open 'extract_files.sh' for writing: $!";
       
       foreach my $filename ( @$filenames ) {
          my $file_contents = do {
             open my $infile_fh, '<:encoding(UTF-8)', $filename 
                or die "Unable to open file '$filename' for reading: $!";
             <$infile_fh>;
          };
    
          print {$outfile_fh} "echo -n '$file_contents' > $filename\n";
       }
       close $outfile_fh;
    
       return;
    }
    make_shell_archive(\@ARGV);
    

    Two sample files: file1 and file2

    file1 contents:
    the quick brown fox jumped over the lazy dog

    file2 contents:
    foo bar baz quux

    Usage:

    perl shell_archive.pl file1 file2
    [hunter@apollo: 08]$ cat extract_files.sh 
    echo -n 'the quick brown fox jumped over the lazy dog' > file1
    echo -n 'foo bar baz quux' > file2
    [hunter@apollo: 08]$ ls
    extract_files.sh  file1  file2  shell_archive.pl  three_hw_qs.sml
    [hunter@apollo: 08]$ rm file*
    [hunter@apollo: 08]$ chmod +x extract_files.sh 
    [hunter@apollo: 08]$ ls 
    extract_files.sh  shell_archive.pl  three_hw_qs.sml
    [hunter@apollo: 08]$ ./extract_files.sh 
    [hunter@apollo: 08]$ ls 
    extract_files.sh  file1  file2  shell_archive.pl  three_hw_qs.sml
    [hunter@apollo: 08]$ cat file1
    the quick brown fox jumped over the lazy dog
    [hunter@apollo: 08]$ cat file2
    foo bar baz quux
    

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