textproc.html

Shall高级编程

  30 
  31 for filename in *    # Not necessary to use basename,
  32                      # since "*" won't return any file containing "/".
  33 do n=`echo "$filename/" | tr '[:upper:]' '[:lower:]'`
  34 #                             POSIX char set notation.
  35 #                    Slash added so that trailing newlines are not
  36 #                    removed by command substitution.
  37    # Variable substitution:
  38    n=${n%/}          # Removes trailing slash, added above, from filename.
  39    [[ $filename == $n ]] || mv "$filename" "$n"
  40                      # Checks if filename already lowercase.
  41 done
  42 
  43&nbsp;exit $?</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
><A
NAME="TRD2U"
></A
></P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="DU"
></A
><P
><B
>Example 15-22. <I
CLASS="FIRSTTERM"
>du</I
>: DOS to UNIX text file conversion.</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# Du.sh: DOS to UNIX text file converter.
   3&nbsp;
   4&nbsp;E_WRONGARGS=65
   5&nbsp;
   6&nbsp;if [ -z "$1" ]
   7&nbsp;then
   8&nbsp;  echo "Usage: `basename $0` filename-to-convert"
   9&nbsp;  exit $E_WRONGARGS
  10&nbsp;fi
  11&nbsp;
  12&nbsp;NEWFILENAME=$1.unx
  13&nbsp;
  14&nbsp;CR='\015'  # Carriage return.
  15&nbsp;           # 015 is octal ASCII code for CR.
  16&nbsp;           # Lines in a DOS text file end in CR-LF.
  17&nbsp;           # Lines in a UNIX text file end in LF only.
  18&nbsp;
  19&nbsp;tr -d $CR &#60; $1 &#62; $NEWFILENAME
  20&nbsp;# Delete CR's and write to new file.
  21&nbsp;
  22&nbsp;echo "Original DOS text file is \"$1\"."
  23&nbsp;echo "Converted UNIX text file is \"$NEWFILENAME\"."
  24&nbsp;
  25&nbsp;exit 0
  26&nbsp;
  27&nbsp;# Exercise:
  28&nbsp;# --------
  29&nbsp;# Change the above script to convert from UNIX to DOS.</PRE
></TD
></TR
></TABLE
><HR></DIV
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="ROT13"
></A
><P
><B
>Example 15-23. <I
CLASS="FIRSTTERM"
>rot13</I
>: ultra-weak encryption.</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# rot13.sh: Classic rot13 algorithm,
   3&nbsp;#           encryption that might fool a 3-year old.
   4&nbsp;
   5&nbsp;# Usage: ./rot13.sh filename
   6&nbsp;# or     ./rot13.sh &#60;filename
   7&nbsp;# or     ./rot13.sh and supply keyboard input (stdin)
   8&nbsp;
   9&nbsp;cat "$@" | tr 'a-zA-Z' 'n-za-mN-ZA-M'   # "a" goes to "n", "b" to "o", etc.
  10&nbsp;#  The 'cat "$@"' construction
  11&nbsp;#+ permits getting input either from stdin or from files.
  12&nbsp;
  13&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="CRYPTOQUOTE"
></A
><P
><B
>Example 15-24. Generating <SPAN
CLASS="QUOTE"
>"Crypto-Quote"</SPAN
> Puzzles</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# crypto-quote.sh: Encrypt quotes
   3&nbsp;
   4&nbsp;#  Will encrypt famous quotes in a simple monoalphabetic substitution.
   5&nbsp;#  The result is similar to the "Crypto Quote" puzzles
   6&nbsp;#+ seen in the Op Ed pages of the Sunday paper.
   7&nbsp;
   8&nbsp;
   9&nbsp;key=ETAOINSHRDLUBCFGJMQPVWZYXK
  10&nbsp;# The "key" is nothing more than a scrambled alphabet.
  11&nbsp;# Changing the "key" changes the encryption.
  12&nbsp;
  13&nbsp;# The 'cat "$@"' construction gets input either from stdin or from files.
  14&nbsp;# If using stdin, terminate input with a Control-D.
  15&nbsp;# Otherwise, specify filename as command-line parameter.
  16&nbsp;
  17&nbsp;cat "$@" | tr "a-z" "A-Z" | tr "A-Z" "$key"
  18&nbsp;#        |  to uppercase  |     encrypt       
  19&nbsp;# Will work on lowercase, uppercase, or mixed-case quotes.
  20&nbsp;# Passes non-alphabetic characters through unchanged.
  21&nbsp;
  22&nbsp;
  23&nbsp;# Try this script with something like:
  24&nbsp;# "Nothing so needs reforming as other people's habits."
  25&nbsp;# --Mark Twain
  26&nbsp;#
  27&nbsp;# Output is:
  28&nbsp;# "CFPHRCS QF CIIOQ MINFMBRCS EQ FPHIM GIFGUI'Q HETRPQ."
  29&nbsp;# --BEML PZERC
  30&nbsp;
  31&nbsp;# To reverse the encryption:
  32&nbsp;# cat "$@" | tr "$key" "A-Z"
  33&nbsp;
  34&nbsp;
  35&nbsp;#  This simple-minded cipher can be broken by an average 12-year old
  36&nbsp;#+ using only pencil and paper.
  37&nbsp;
  38&nbsp;exit 0
  39&nbsp;
  40&nbsp;#  Exercise:
  41&nbsp;#  --------
  42&nbsp;#  Modify the script so that it will either encrypt or decrypt,
  43&nbsp;#+ depending on command-line argument(s).</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
><A
NAME="TRVARIANTS"
></A
></P
><TABLE
CLASS="SIDEBAR"
BORDER="1"
CELLPADDING="5"
><TR
><TD
><DIV
CLASS="SIDEBAR"
><A
NAME="AEN10567"
></A
><P
><B
><I
CLASS="FIRSTTERM"
>tr</I
> variants</B
></P
><P
>	    The <B
CLASS="COMMAND"
>tr</B
> utility has two historic
	    variants. The BSD version does not use brackets
	    (<TT
CLASS="USERINPUT"
><B
>tr a-z A-Z</B
></TT
>), but the SysV one does
	    (<TT
CLASS="USERINPUT"
><B
>tr '[a-z]' '[A-Z]'</B
></TT
>). The GNU version
	    of <B
CLASS="COMMAND"
>tr</B
> resembles the BSD one.
	    </P
></DIV
></TD
></TR
></TABLE
></DD
><DT
><A
NAME="FOLDREF"
></A
><B
CLASS="COMMAND"
>fold</B
></DT
><DD
><P
>A filter that wraps lines of input to a specified width.
	      This is especially useful with the <TT
CLASS="OPTION"
>-s</TT
>
	      option, which breaks lines at word spaces (see <A
HREF="textproc.html#EX50"
>Example 15-25</A
> and <A
HREF="contributed-scripts.html#MAILFORMAT"
>Example A-1</A
>).</P
></DD
><DT
><A
NAME="FMTREF"
></A
><B
CLASS="COMMAND"
>fmt</B
></DT
><DD
><P
>Simple-minded file formatter, used as a filter in a
	      pipe to <SPAN
CLASS="QUOTE"
>"wrap"</SPAN
> long lines of text
	      output.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="EX50"
></A
><P
><B
>Example 15-25. Formatted file listing.</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;
   3&nbsp;WIDTH=40                    # 40 columns wide.
   4&nbsp;
   5&nbsp;b=`ls /usr/local/bin`       # Get a file listing...
   6&nbsp;
   7&nbsp;echo $b | fmt -w $WIDTH
   8&nbsp;
   9&nbsp;# Could also have been done by
  10&nbsp;#    echo $b | fold - -s -w $WIDTH
  11&nbsp; 
  12&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
>See also <A
HREF="moreadv.html#EX41"
>Example 15-5</A
>.</P
><DIV
CLASS="TIP"
><TABLE
CLASS="TIP"
WIDTH="90%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="common/tip.png"
HSPACE="5"
ALT="Tip"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>A powerful alternative to <B
CLASS="COMMAND"
>fmt</B
> is
	      Kamil Toman's <B
CLASS="COMMAND"
>par</B
>
	      utility, available from <A
HREF="http://www.cs.berkeley.edu/~amc/Par/"
TARGET="_top"
>http://www.cs.berkeley.edu/~amc/Par/</A
>.
	      </P
></TD
></TR
></TABLE
></DIV
></DD
><DT
><A
NAME="COLREF"
></A
><B
CLASS="COMMAND"
>col</B
></DT
><DD
><P
>This deceptively named filter removes reverse line feeds
	      from an input stream. It also attempts to replace
	      whitespace with equivalent tabs. The chief use of
	      <B
CLASS="COMMAND"
>col</B
> is in filtering the output
	      from certain text processing utilities, such as
	      <B
CLASS="COMMAND"
>groff</B
> and <B
CLASS="COMMAND"
>tbl</B
>.</P
></DD
><DT
><A
NAME="COLUMNREF"
></A
><B
CLASS="COMMAND"
>column</B
></DT
><DD
><P
>Column formatter. This filter transforms list-type
	      text output into a <SPAN
CLASS="QUOTE"
>"pretty-printed"</SPAN
> table
	      by inserting tabs at appropriate places.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="COL"
></A
><P
><B
>Example 15-26. Using <I
CLASS="FIRSTTERM"
>column</I
> to format a directory
	        listing</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# This is a slight modification of the example file in the "column" man page.
   3&nbsp;
   4&nbsp;
   5&nbsp;(printf "PERMISSIONS LINKS OWNER GROUP SIZE MONTH DAY HH:MM PROG-NAME\n" \
   6&nbsp;; ls -l | sed 1d) | column -t
   7&nbsp;
   8&nbsp;#  The "sed 1d" in the pipe deletes the first line of output,
   9&nbsp;#+ which would be "total        N",
  10&nbsp;#+ where "N" is the total number of files found by "ls -l".
  11&nbsp;
  12&nbsp;# The -t option to "column" pretty-prints a table.
  13&nbsp;
  14&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
></DD
><DT
><A
NAME="COLRMREF"
></A
><B
CLASS="COMMAND"
>colrm</B
></DT
><DD
><P
>Column removal filter. This removes columns (characters)
	      from a file and writes the file, lacking the range of
	      specified columns, back to <TT
CLASS="FILENAME"
>stdout</TT
>.
	      <TT
CLASS="USERINPUT"
><B
>colrm 2 4 &#60;filename</B
></TT
> removes the
	      second through fourth characters from each line of the
	      text file <TT
CLASS="FILENAME"
>filename</TT
>.</P
><DIV
CLASS="CAUTION"
><TABLE
CLASS="CAUTION"
WIDTH="90%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="common/caution.png"
HSPACE="5"
ALT="Caution"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>If the file contains tabs or nonprintable
	      characters, this may cause unpredictable
	      behavior. In such cases, consider using
	      <A
HREF="textproc.html#EXPANDREF"
>expand</A
> and
	      <B
CLASS="COMMAND"
>unexpand</B
> in a pipe preceding
	      <B
CLASS="COMMAND"
>colrm</B
>.</P
></TD
></TR
></TABLE
></DIV
></DD
><DT
><A
NAME="NLREF"
></A
><B
CLASS="COMMAND"
>nl</B
></DT
><DD
><P
>Line numbering filter: <TT
CLASS="USERINPUT"
><B
>nl filename</B
></TT
>
	    lists <TT
CLASS="FILENAME"
>filename</TT
> to
	    <TT
CLASS="FILENAME"
>stdout</TT
>, but inserts consecutive
	    numbers at the beginning of each non-blank line. If
	    <TT
CLASS="FILENAME"
>filename</TT
> omitted, operates on
	    <TT
CLASS="FILENAME"
>stdin.</TT
></P
><P
>The output of <B
CLASS="COMMAND"
>nl</B
> is very similar to
	      <TT
CLASS="USERINPUT"
><B
>cat -b</B
></TT
>, since, by default
	      <B
CLASS="COMMAND"
>nl</B
> does not list blank lines.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="LNUM"
></A
><P
><B
>Example 15-27. <I
CLASS="FIRSTTERM"
>nl</I
>: A self-numbering script.</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# line-number.sh
   3&nbsp;
   4&nbsp;# This script echoes itself twice to stdout with its lines numbered.
   5&nbsp;
   6&nbsp;# 'nl' sees this as line 4 since it does not number blank lines.
   7&nbsp;# 'cat -n' sees the above line as number 6.
   8&nbsp;
   9&nbsp;nl `basename $0`
  10&nbsp;
  11&nbsp;echo; echo  # Now, let's try it with 'cat -n'
  12&nbsp;
  13&nbsp;cat -n `basename $0`
  14&nbsp;# The difference is that 'cat -n' numbers the blank lines.
  15&nbsp;# Note that 'nl -ba' will also do so.
  16&nbsp;
  17&nbsp;exit 0
  18&nbsp;# -----------------------------------------------------------------</PRE
></TD
></TR
></TABLE
><HR></DIV
></DD
><DT
><A
NAME="PRREF"
></A
><B
CLASS="COMMAND"
>pr</B
></DT
><DD
><P
>Print formatting filter. This will paginate files
	      (or <TT
CLASS="FILENAME"
>stdout</TT
>) into sections suitable for
	      hard copy printing or viewing on screen.	Various options
	      permit row and column manipulation, joining lines, setting
	      margins, numbering lines, adding page headers, and merging
	      files, among other things. The <B
CLASS="COMMAND"
>pr</B
>
	      command combines much of the functionality of
	      <B
CLASS="COMMAND"
>nl</B
>, <B
CLASS="COMMAND"
>paste</B
>,
	      <B
CLASS="COMMAND"
>fold</B
>, <B
CLASS="COMMAND"
>column</B
>, and
	      <B
CLASS="COMMAND"
>expand</B
>.</P
><P
><TT
CLASS="USERINPUT"
><B
>pr -o 5 --width=65 fileZZZ | more</B
></TT
>
	     gives a nice paginated listing to screen of
	     <TT
CLASS="FILENAME"
>fileZZZ</TT
> with margins set at 5 and
	     65.</P
><P
>A particularly useful option is <TT
CLASS="OPTION"
>-d</TT
>,
	      forcing double-spacing (same effect as <B
CLASS="COMMAND"
>sed
	      -G</B
>).</P
></DD
><DT
><A
NAME="GETTEXTREF"
></A
><B
CLASS="COMMAND"
>gettext</B
></DT
><DD
><P
>The GNU <B
CLASS="COMMAND"
>gettext</B
> package is a set of
	      utilities for <A
HREF="localization.html"
>localizing</A
>
	      and translating the text output of programs into foreign
	      languages. While originally intended for C programs, it
	      now supports quite a number of programming and scripting
	      languages.</P
><P
>The  <B
CLASS="COMMAND"
>gettext</B
>
	      <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>program</I
></SPAN
> works on shell scripts. See
	      the <TT
CLASS="REPLACEABLE"
><I
>info page</I
></TT
>.</P
></DD
><DT
><A
NAME="MSGFMTREF"
></A
><B
CLASS="COMMAND"
>msgfmt</B
></DT
><DD
><P
>A program for generating binary
	      message catalogs. It is used for <A
HREF="localization.html"
>localization</A
>.</P
></DD
><DT
><A
NAME="ICONVREF"
></A
><B
CLASS="COMMAND"
>iconv</B
></DT
><DD
><P
>A utility for converting file(s) to a different encoding