colline.sh : convert column to line with optional delimiter string.

colline.sh

#!/usr/bin/env bash
#              bash 3.2.25(1)    Ubuntu 7.10                   Date : 2012-03-25
#
# _______________|  colline : convert column to line with optional delimiter.
#
#           Usage:  colline  [file]  [delimiter]
#                                     ^space as default; string is acceptable.
#                             ^assuming each line represents one column.
#
#    Dependencies:  awk, sed  
#
#             Tip:  If file is multi-column, consider using my:
#                       <( field ... )    # with process substitution.
#
#  CHANGE LOG  LATEST version available:   https://bitbucket.org/rsvp/gists/src
#  2012-03-25  Rewrite using awk resolving the previous bug
#                 which squeezed spaces and also prevented removal 
#                 of the last delimiter in some cases.
#  2012-03-24  Change default file to stdin; add case for personal shortcuts.
#                 Add colline to gists repository.
#  2010-05-29  Second version eliminates disk usage via echo variable.
#  2010-05-28  First version for a very common task with tedious details.

#           _____ Prelims
set -u
#   ^ unbound (i.e. unassigned) variables are treated as error.
#           Example of default assignment:    arg1=${1:-'foo'}
set -e
#   ^ error checking :: Highly Recommended (caveat:  you can't check $? later).  
#
# _______________     ::  BEGIN  Script ::::::::::::::::::::::::::::::::::::::::

arg1=${1:-'-'}
arg2=${2:-' '}
#          ^space as default DELIMITER STRING.
#           Avoid use of double quote character within any such string 
#              since that conflicts with awk's printf statement.
#              Remedy: consider quotel in gists repository to preprocess.
arg2=${arg2//\~/\\~}
#          ^^escape all occurences of tilde ~ within delimiter string
#              else sed will complain due to its internal separator
#              (ignore awk's warning to stderr).


case "$arg1" in 
     #      handy personal abbreviations for filenames 
     'p')   arg1='/tmp/pye.tmp'                               ;;
esac


#      __________ AWK within a bash script
#                 Here Document serves as its program file.
#                 Bash variables are recognized, so escape awk field numbers.
{ awk -f -  <(cat "$arg1")  <<EOHereDoc
     { printf "%s$arg2", \$0 }
     #                ^here printf does not automatically add newline.
     #        ^at the end of each record \$0, append the delimiter string.
     END { printf "\n" }
EOHereDoc
} |  sed "s~${arg2}$~~"  
#         ^delete the last unnecessary delimiter from awk output.


exit 0
# _______________ EOS ::  END of Script ::::::::::::::::::::::::::::::::::::::::

#  Moral: Do not use echo if string fidelity is crucial.

#  vim: set fileencoding=utf-8 ff=unix tw=78 ai syn=sh :