#!/usr/bin/nawk -f
# To run this script, type: nawk_intro.nawk
# Do not include a file name or anything else after the command
# Note: Esc [ H Esc [ J is the tput code to clear screen on Solaris

BEGIN{print "Image this is a line from a data file:\n\n\n\n\n\n"
      print "The rain in Spain falls mainly on the plain!"
}

NR==1{printf"\n\n\n\nThis is how nawk interprets it:"}
NR==2{printf"\n\n\n"
      print "+------------------- $0 -------------------+"
      print "|                                          |"
      print "v                                          v\n"
      print "The rain in Spain falls mainly on the plain!\n"
      print " ^   ^   ^    ^     ^     ^    ^   ^    ^"
      print " |   |   |    |     |     |    |   |    |"
      print "$1  $2  $3   $4    $5    $6   $7  $8   $9\n"
}

NR==3{printf"NAWK is a 'pattern { ACTION }' scripting language:"}
NR==4{printf"\n where pattern can be specified as an "
      printf"extended Regular Expression"
}
NR==5{print " such as: /^[Tt]he [a-z]+ in Spain.*!$/"}
NR==6{printf" pattern can also be specified as a condition: $4 == \"Spain\""}
NR==7{printf"\n\n\nDo you think we can specify a pattern and no ACTION?"}
NR==8{print " such as: /Spain/"}
NR==9{printf"The default ACTION is to print the line: { print $0 }"}
NR==10{print " resulting in: /Spain/ { print $0 }"}
NR==11{printf"Do you think we can specify an { ACTION } only?"}
NR==12{print " such as: { print $1 }"}
NR==13{printf"{ ACTION } will apply to all lines to the file."}

NR==14{print "\n"
       print " pattern { ACTION }\n"
       print " ^                ^"
       print " |                |"
       print " +----- Rule -----+\n"
}

NR==15{printf"Here is a complete list of NAWK's built-in variables:"}
NR==16{print "\n"
       print "NF       - Number of fields in current record"
       print "RS       - Input record separator  (newline)"
       print "FS       - Input field separator  (spaces/tabs)"
       print "NR       - Number of records from beginning of first input file"
       print "OFS      - Output field separator (space)"
       print "ORS      - Output record separator (newline)"
       print "FNR      - Number of records from beginning of current file"
       print "OFMT     - Output format for numbers (%.6g)"
       print "ARGC     - Number of command line arguments"
       print "ARGV     - Array of command line arguments"
       print "FILENAME - Current input filename"
       print "RSTART   - Index into a string, set by match()"
       print "RLENGTH  - Length of a substring, set by match()"
       print "CONVFMT  - String conversion format for numbers (%.6g)"
       print "ENVIRON  - Associative array for environment variables"
       print "SUBSEP   - Separator character for array subscripts (\\034)\n"
}
NR==17{printf"For example, this one-liner interpolate's the shell's global "
       print "PATH variable:"
}
NR==18{print "nawk 'BEGIN{print ENVIRON[\"PATH\"]}'"}
NR==19{printf"%s\n",ENVIRON["PATH"]}
NR==20{printf"\nHere is how to find the many implementations of AWK:"}
NR==21{print ""
       print "awk/nawk: ls /usr/bin/*awk*"
       print "gawk: http://www.gnu.org/software/gawk/gawk.html"
       print "GNU Awk User's Guide: http://www.gnu.org/manual/gawk/index.html"
       printf"Edition 3 of GAWK: Effective AWK Programming: "
       print "A User's Guide for GNU Awk:"
       print " http://www.gnu.org/manual/gawk-3.1.1/html_mono/gawk.html"
       print "tawk: http://www.tasoft.com/tawk.html"
       print "mawk (Mike Brennan awk): ftp://ftp.whidbey.net/pub/brennan"
       print "mksawk (part of the MKS Toolkit): http://www.mkssoftware.com/"
       print "       http://www.mkssoftware.com/docs/man1/awk.1.asp"
       print "       http://www.mkssoftware.com/docs/man1/awkc.1.asp"
       printf"awkcc (an awk compiler to C): previously at "
       print "http://www.unipress.com/att"
       print "awkc++: http://cm.bell-labs.com/cm/cs/who/bwk"
       print "awka: http://awka.sourceforge.net"
       print "awk2c: ftp://sunsite.unc.edu/pub/Linux/utils/text/awk2c050.tgz"
       print "a2p (awk to perl): ls /usr/perl5/bin/a2p"
       print "A great awk faq: http://www.faqs.org/faqs/computer-lang/awk/faq"
       printf"The GAWK pdf reference guide: "
       print "http://torvalds.cs.mtsu.edu/~neal/awkcard.pdf\n"
}

NR==22{printf"Here are the limitations to NAWK/AWK:"}
NR==23{print "  100 fields"
       print " 2500 chars per input record"
       print " 2500 chars per output record"
       print " 1024 chars per field"
       print " 1024 chars per printf string"
       print "  400 chars max literal string"
       print "  400 chars in char class"
       print "   15 open files"
       print "    1 pipe"
       print " double-precision floating point"
}

NR==24{print "\n\nHappy Nawk scripting!\n"; exit}

END{print "Warning:\n"
    print "too much NAWKing might make you into a NAWKaholic!\n"
}