第12章 Programming

目次

12.1. シェルスクリプト
12.1.1. POSIX shell compatibility
12.1.2. シェル変数
12.1.3. Shell conditionals
12.1.4. シェルループ
12.1.5. The shell command-line processing sequence
12.1.6. Utility programs for shell script
12.1.7. Shell script dialog
12.1.8. Shell script example with zenity
12.2. Make
12.3. C
12.3.1. Simple C program (gcc)
12.3.2. Debugging with gdb
12.3.2.1. 基本的なgdb実行
12.3.2.2. Debianパッケージのデバグ
12.3.2.3. Obtaining backtrace
12.3.2.4. Advanced gdb commands
12.3.2.5. Debugging X Errors
12.3.3. ライブラリーへの依存の確認
12.3.4. Debugging with memory leak detection tools
12.3.5. Disassemble binary
12.3.6. Flex — a better Lex
12.3.7. Bison — a better Yacc
12.4. Autoconf
12.4.1. Compile and install a program
12.4.2. Uninstall program
12.5. Perl short script madness
12.6. Web
12.7. Static code analysis tools
12.8. ソースコード変換
12.9. Debianパッケージ作成

I provide some pointers for people to learn programming on the Debian system enough to trace the packaged source code. Here are notable packages and corresponding documentation packages for programing.

表12.1 プログラムをすることを補助するパッケージのリスト。

パッケージ popcon サイズ 文書
autoconf V:4, I:26 1868 "info autoconf" provided by autoconf-doc
automake V:3, I:18 1716 "info automake" provided by automake1.10-doc
bash V:91, I:99 1336 "info bash" provided by bash-doc
bison V:2, I:17 1820 "info bison" provided by bison-doc
cpp V:45, I:85 76 "info cpp" provided by cpp-doc
ddd V:0.4, I:3 4104 "info ddd" provided by ddd-doc
exuberant-ctags V:1.3, I:6 288 exuberant-ctags(1)
flex V:2, I:17 1004 "info flex" provided by flex-doc
gawk V:24, I:28 2116 "info gawk" provided by gawk-doc
gcc V:18, I:69 64 "info gcc" provided by gcc-doc
gdb V:6, I:34 7128 "info gdb" provided by gdb-doc
gettext V:9, I:51 7856 "info gettext" provided by gettext-doc
gfortran V:1.3, I:6 40 "info gfortran" provided by gfortran-doc
glade V:0.4, I:2 1397 Help provided via menu
glade-gnome V:0.17, I:1.5 434 Help provided via menu
libc6 V:95, I:99 11496 "info libc" provided by glibc-doc and glibc-doc-reference
make V:22, I:76 1220 "info make" provided by make-doc
mawk V:69, I:99 248 mawk(1)
perl V:89, I:99 18824 perl(1) and html pages provided by perl-doc and perl-doc-html
python V:62, I:96 620 python(1) and html pages provided by python-doc
tcl8.4 V:8, I:45 3336 tcl(3) and detail manual pages provided by tcl8.4-doc
tk8.4 V:6, I:35 2800 tk(3) and detail manual pages provided by tk8.4-doc
ruby V:10, I:25 100 ruby(1) and interactive reference provided by ri
vim V:14, I:30 1740 Help(F1) menu provided by vim-doc
susv2 I:0.03 48 Fetch "The Single Unix Specifications v2"
susv3 I:0.09 48 Fetch "The Single Unix Specifications v3"

Online references are available by typing "man name" after installing manpages and manpages-dev packages. Online references for the GNU tools are available by typing "info program_name" after installing the pertinent documentation packages. You may need to include the contrib and non-free archives in addition to the main archive since some GFDL documentations are not considered to be DSFG compliant.

[警告] 警告

Do not use "test" as the name of an executable test file. "test" is a shell builtin.

[注意] 注意

ソースから直接コンパイルしたソフトウエアプログラムは、システムプログラムとかち合わないように、"/usr/local"か"/opt"の中にインストールしましょう。

[ティップ] ティップ

Code examples of creating "Song 99 Bottles of Beer" should give you good idea of practically all the programming languages.

12.1. シェルスクリプト

The shell script is a text file with the execution bit set and contains the commands in the following format.

#!/bin/sh
... command lines ...

The first line specifies the shell interpreter which read and execute this file contents.

Reading shell scripts is the best way to understand how a Unix-like system works. Here, I give some pointers and reminders for shell programming. See "Shell Mistakes" (http://www.greenend.org.uk/rjk/2001/04/shell.html) to learn from mistakes.

Unlike shell interactive mode (see 「シェルプロンプト」 and 「Unix的テキスト処理」), parameters, conditionals, and loops are used frequently.

12.1.1. POSIX shell compatibility

Many system scripts may be interpreted by any one of POSIX shells (see 表1.14「シェルプログラムのリスト。」). The default shell for the system is "/bin/sh" which is a symlink pointing to the actual program:

  • bash(1) for lenny or older.
  • dash(1) for squeeze or newer.

Avoid writing a shell script with "bashisms" or "zshisms" to make it portable among all POSIX shells. You can check it using checkbashisms(1).

表12.2 List of typical bashisms.

Good: POSIX Avoid: bashism
if [ "$foo" = "$bar" ] ; then … if [ "$foo" == "$bar" ] ; then …
diff -u file.c.orig file.c diff -u file.c{.orig,}
mkdir /foobar /foobaz mkdir /foo{bar,baz}
octal format: "\377" hexadecimal format: "\xff"

The "echo" command must be used with care since its implementation differs among shell builtin commands and external command:

  • Avoid using any command options except "-n". (Notably avoid "-e" and "-E")
  • Avoid using escape sequences in the string since their handling varies.
[注意] 注意

Although "-n option is not really POSIX syntax, it is generally accepted.

[ティップ] ティップ

Use the "printf" command instead of the "echo" command if you need to embed escape sequences in the output string.

12.1.2. シェル変数

Special shell parameters are frequently used in the shell script:

表12.3 シェル変数のリスト。

シェル変数 変数値
$0 シェルまたはシェルスクリプトの名前
$1 最初(1番目)のシェル引数
$9 9番目のシェル引数
$# シェル引数の数
"$*" "$1 $2 $3 $4 … "
"$@" "$1" "$2" "$3" "$4" …
$? 最近実行のコマンドの終了状態
$$ このシェルスクリプトのPID
$! 最近スタートしたバックグラウンドジョブのPID

覚えておくべき基本的なパラメータ展開:

表12.4 List of shell parameter expansions.

parameter expression form value if var is set value if var is not set
${var:-string} "$var" "string"
${var:+string} "string" "null"
${var:=string} "$var" "string" (and run "var=string")
${var:?string} "$var" echo "string" to stderr (and exit with error)

Here, the colon ":" in all of these operators is actually optional.

  • With ":" = operator test for exist and not null.
  • Without ":" = operator test for exist only.

表12.5 List of key shell parameter substitutions.

parameter substitution form Result
${var%suffix} Remove smallest suffix pattern
${var%%suffix} Remove largest suffix pattern
${var#prefix} Remove smallest prefix pattern
${var##prefix} Remove largest prefix pattern

12.1.3. Shell conditionals

Each command returns an exit status which can be used for conditional expressions:

  • Success: 0 (True)
  • Error: 1--255 (False) Note that the use here of a 0 value to mean "true" differs from the usual convention in some other areas of computing. Also, "[" is the equivalent of the test command, which evaluates its arguments up to "]" as a conditional expression.

覚えておくべき基本的な定形条件文は次です:

  • "<command> && <if_success_run_this_command_too> || true",
  • "<command> || <if_not_success_run_this_command_too> || true", and
  • a multi-line script snippet:
if [ <conditional_expression> ]; then
 <if_success_run_this_command>
else
 <if_not_success_run_this_command>
fi

Here trailing "|| true" was needed to ensure this shell script will not exit at this line accidentally when shell is invoked with "-e" flag.

表12.6 List of file comparison operators in the conditional expression.

equation 変数値
-e <file> True if <file> exists.
-d <file> True if <file> exists and is a directory.
-f <file> True if <file> exists and is a regular file.
-w <file> True if <file> exists and is writable.
-x <file> True if <file> exists and is executable.
<file1> -nt <file2> True if <file1> is newer than <file2>. (modification).
<file1> -ot <file2> True if <file1> is older than <file2>. (modification).
<file1> -ef <file2> True if they are the same device and inode number.

表12.7 List of string comparison operators in the conditional expression.

equation 変数値
-z <str> True if the length of <str> is zero.
-n <str> True if the length of <str> is non-zero.
<str1> = <str2> True if <str1> and <str2> are equal.
<str1> != <str2> True if <str1> and <str2> are not equal.
<str1> < <str2> True if <str1> sorts before <str2>. (locale dependent)
<str1> > <str2> True if <str1> sorts after <str2>. (locale dependent)

Arithmetic integer comparison operators in the conditional expression are "-eq", "-ne", "-lt", "-le", "-gt", and "-ge".

12.1.4. シェルループ

There are several loop idioms to use in POSIX shell:

  • "for name in word ; do list ; done": loops over list of words.
  • "while list; do list; done": repeats while true.
  • "until list; do list; done": repeats while not true.
  • "break": enables to exit from the loop.
  • "continue" enables to resume the next iteration of the loop.
[ティップ] ティップ

The C-language like numeric iteration can be realized by using seq(1) as the "word" generator.

12.1.5. The shell command-line processing sequence

The shell processes a script as following sequence:

  • split line into tokens by the metacharacters: SPACE TAB NEWLINE ; ( ) < > | &
  • check keyword if not within "…" or '…' (loop)
  • expand alias if not within "…" or '…' (loop)
  • expand tilde, "~<user>" → <user>'s home directory, if not within "…" or '…'
  • expand parameter, "$PARAMETER", if not within '…'
  • expand command substitution, "$( command )", if not within '…'
  • split into words with "$IFS" if not within "…" or '…'
  • expand * ? [ ] in pathname if not within "…" or '…'
  • コマンド次から検索します:

    • 関数定義
    • ビルトインコマンド
    • "$PATH"中の実行ファイル
  • go to the next line and repeat this process again from the top of this sequence

Single quotes within double quotes have no effect.

Executing "set -x" in the shell or invoking the shell with "-x" option make the shell to print all of commands executed. This is quite handy for debugging.

12.1.6. Utility programs for shell script

In order to make your shell program as portable as possible across Debian system, it is good idea to limit utility programs used within Essential programs listed by "aptitude search ~E" as much as possible.

coreutils, bsdutils, and debianutils packages contain many useful small utilities.

12.1.7. Shell script dialog

The user interface of a simple shell program can be improved from dull interaction by echo and read commands to more interactive one by using one of the so-called dialog program etc.

表12.8 List of user interface programs.

パッケージ popcon サイズ 機能
x11-utils V:21, I:46 644 xmessage(1) displays a message or query in a window. (X)
whiptail V:49, I:99 64 displays user-friendly dialog boxes from shell scripts. (newt)
dialog V:5, I:24 1508 displays user-friendly dialog boxes from shell scripts. (ncurses)
zenity V:6, I:46 4032 display graphical dialog boxes from shell scripts. (gtk2.0)
gtkdialog V:0.07, I:0.3 488 GUI-creation command-line utility based on GTK+ library. (gtk2.0+glade2)
ssft V:0.01, I:0.12 152 Shell Scripts Frontend Tool. (wrapper for zenity, kdialog, and dialog with gettext)
gettext V:9, I:51 7856 "/usr/bin/gettext.sh" for translate message

12.1.8. Shell script example with zenity

Here is a simple script which creates ISO image with RS02 data supplemented by dvdisaster(1):

#!/bin/sh -e
# gmkrs02 : Copyright (C) 2007 Osamu Aoki <osamu@debian.org>, Public Domain
#set -x
error_exit()
{
  echo "$1" >&2
  exit 1
}
# Initialize variables
DATA_ISO="$HOME/Desktop/iso-$$.img"
LABEL=$(date +%Y%m%d-%H%M%S-%Z)
if [ $# != 0 ] && [ -d "$1" ]; then
  DATA_SRC="$1"
else
  # Select directory for creating ISO image from folder on desktop
  DATA_SRC=$(zenity --file-selection --directory  \
    --title="Select the directory tree root to create ISO image") \
    || error_exit "Exit on directory selection"
fi
# Check size of archive
xterm -T "Check size $DATA_SRC" -e du -s $DATA_SRC/*
SIZE=$(($(du -s $DATA_SRC | awk '{print $1}')/1024))
if [ $SIZE -le 520 ] ; then
  zenity --info --title="Dvdisaster RS02" --width 640  --height 400 \
    --text="The data size is good for CD backup:\\n $SIZE MB"
elif [ $SIZE -le 3500 ]; then
  zenity --info --title="Dvdisaster RS02" --width 640  --height 400 \
    --text="The data size is good for DVD backup :\\n $SIZE MB"
else
  zenity --info --title="Dvdisaster RS02" --width 640  --height 400 \
    --text="The data size is too big to backup : $SIZE MB"
  error_exit "The data size is too big to backup :\\n $SIZE MB"
fi
# only xterm is sure to have working -e option
# Create raw ISO image
rm -f "$DATA_ISO" || true
xterm -T "genisoimage $DATA_ISO" \
  -e genisoimage -r -J -V "$LABEL" -o "$DATA_ISO" "$DATA_SRC"
# Create RS02 supplemental redundancy
xterm -T "dvdisaster $DATA_ISO" -e  dvdisaster -i "$DATA_ISO" -mRS02 -c
zenity --info --title="Dvdisaster RS02" --width 640  --height 400 \
  --text="ISO/RS02 data ($SIZE MB) \\n created at: $DATA_ISO"
# EOF

You may wish to create launcher on the desktop with command set something like "/usr/local/bin/gmkrs02 %d".

12.2. Make

Make is a utility to maintain groups of programs. Upon execution of make(1), make read the rule file, "Makefile", and updates a target if it depends on prerequisite files that have been modified since the target was last modified, or if the target does not exist. The execution of these updates may occur concurrently.

The rule file syntax is :

target: [ prerequisites ... ]
 [TAB]  command1
 [TAB]  -command2 # ignore errors
 [TAB]  @command3 # suppress echoing

Here " [TAB] " is a TAB code. Each line is interpreted by the shell after make variable substitution. Use "\" at the end of a line to continue the script. Use "$$" to enter "$" for environment values for a shell script.

Implicit rules for the target and prerequisites can be written, for example, as:

%.o: %.c header.h

Here, the target contains the character "%" (exactly one of them). The "%" can match any nonempty substring in the actual target filenames. The prerequisites likewise use "%" to show how their names relate to the actual target name.

表12.9 makeの自動変数のリスト。

自動変数 変数値
$@ ターゲット
$< 最初の前提条件
$? 全ての新規の前提条件
$^ 全ての前提条件
$* "%"はターゲットパターンの軸にマッチします

表12.10 make変数の展開のリスト。

変数展開 説明
foo1 := bar 一回だけの展開
foo2 = bar 再帰的展開
foo3 += bar 後ろに追加

Run "make -p -f/dev/null" to see automatic internal rules.

12.3. C

You can set up proper environment to compile programs written in the C programming language by:

# aptitude install glibc-doc manpages-dev libc6-dev gcc build-essential

The libc6-dev package, i.e., GNU C Library, provides C standard library which is collection of header files and library routines used by the C programming language.

References for C:

  • "info libc" (C library function reference)
  • gcc(1) and "info gcc"
  • each_C_library_function_name(3)
  • Kernighan &amp; Ritchie, "The C Programming Language", 2nd edition (Prentice Hall).

12.3.1. Simple C program (gcc)

A simple example "example.c" is compiled with a library "libm" into an executable "run_example":

$ cat > example.c << EOF
#include <stdio.h>
#include <math.h>
#include <string.h>

int main(int argc, char **argv, char **envp){
        double x;
        char y[11];
        x=sqrt(argc+7.5);
        strncpy(y, argv[0], 10); /* prevent buffer overflow */
        y[10] = '\0'; /* fill to make sure string ends with '\0' */
        printf("%5i, %5.3f, %10s, %10s\n", argc, x, y, argv[1]);
        return 0;
}
EOF
$ gcc -Wall -g -o run_example example.c -lm
$ ./run_example
        1, 2.915, ./run_exam,     (null)
$ ./run_example 1234567890qwerty
        2, 3.082, ./run_exam, 1234567890qwerty

Here, "-lm" is needed to link library "/usr/lib/libm.so" from the libc6 package for sqrt(3). The actual library is in "/lib/" with filename "libm.so.6", which is a symlink to "libm-2.7.so".

Look at the last parameter in the output text. There are more than 10 characters even though "%10s" is specified.

The use of pointer memory operation functions without boundary checks, such as sprintf(3) and strcpy(3), is deprecated to prevent buffer overflow exploits that leverage the above overrun effects. Instead, use snprintf(3) and strncpy(3).

12.3.2. Debugging with gdb

In order to be a good Debian user, you must be able to produce meaningful bug report using debugger. The fist step is to install gdb:

# aptitude install gdb gdb-doc build-essential devscripts

Good tutorial of gdb is provided by "info gdb" or found elsewhere on the web.

12.3.2.1. 基本的なgdb実行

Here is a simple example of using gdb(1) on a "program" compiled with the "-g" option to produce debugging information.

$ gdb program
(gdb) b 1                # set break point at line 1
(gdb) run args           # run program with args
(gdb) next               # next line
...
(gdb) step               # step forward
...
(gdb) p parm             # print parm
...
(gdb) p parm=12          # set value to 12
...
(gdb) quit
[ティップ] ティップ

Many gdb commands can be abbreviated. Tab expansion works as in the shell.

12.3.2.2. Debianパッケージのデバグ

Since all installed binaries should be stripped on the Debian system by default, most debugging symbols are removed in the normal package. In order to debug Debian packages with gdb(1), corresponding *-dbg packages need to be installed (e.g. libc6-dbg in the case of libc6).

If a package to be debugged does not provide its *-dbg package, you need to install it after rebuilding it:

$ mkdir /path/new ; cd /path/new
$ sudo aptitude update
$ sudo aptitude dist-upgrade
$ sudo aptitude install fakeroot devscripts build-essential
$ sudo apt-get build-dep source_package_name
$ apt-get source package_name
$ cd package_name*
  • fix bugs if needed.
$ dch -i
  • bump package version to one which does not collide with official Debian versions, e.g. one appended with "+debug1" when recompiling existing package version, or one appended with "~pre1" when compiling unreleased package version.
$ export DEB_BUILD_OPTIONS=nostrip,noopt
$ debuild
$ cd ..
$ sudo debi package_name*.changes

You need to check build scripts of the package and ensure to use "CFLAGS=-g -Wall" for compiling binaries.

12.3.2.3. Obtaining backtrace

When you encounter program crash, reporting bug report with cut-and-pasted backtrace information is a good idea.

The backtrace can be obtained by the following steps:

  • run the program under gdb(1),
  • reproduce crash (causing you to be dropped back to the gdb prompt), and
  • type "bt" at the gdb prompt.

In case of program freeze, you can crash the program by pressing Ctrl-C in the terminal running gdb to obtain gdb prompt.

[ティップ] ティップ

Often, you will see a backtrace where one or more of the top lines is in "malloc()" or "g_malloc()". When this happens, chances are your backtrace isn't very useful. The easiest way to find some useful information is to set the environment variable "$MALLOC_CHECK_" to a value of 2 (malloc(3)). You can do this while running gdb by doing this:

 $ MALLOC_CHECK_=2 gdb hello

12.3.2.4. Advanced gdb commands

表12.11 上級のgdbコマンドのリスト

objective commands
To get a backtrace for all threads for multi-threaded program. (gdb) thread apply all bt
To get parameters came on the stack of function calls. (gdb) bt full
To get a backtrace and parameters as the combination of the preceding options. (gdb) thread apply all bt full
To get them for top 10 calls to cut off irrelevant output. (gdb) thread apply all bt full 10
To write log of gdb output to a file (the default is gdb.txt). (gdb) set logging on

12.3.2.5. Debugging X Errors

If the GNOME program has received an X error; i.e. you see a message of the form:

The program 'preview1' received an X Window System error.

then you can try running the program with "--sync", and break on the "gdk_x_error" function in order to obtain a backtrace.

12.3.3. ライブラリーへの依存の確認

Use ldd(1) to find out a program's dependency on libraries:

$ ldd /bin/ls
        librt.so.1 => /lib/librt.so.1 (0x4001e000)
        libc.so.6 => /lib/libc.so.6 (0x40030000)
        libpthread.so.0 => /lib/libpthread.so.0 (0x40153000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

For ls(1) to work in a `chroot`ed environment, the above libraries must be available in your `chroot`ed environment.

See also 「Trace program activities」.

12.3.4. Debugging with memory leak detection tools

There are several memory leak detection tools available in Debian.

表12.12 List of memory leak detection tools

パッケージ popcon サイズ 説明
libc6-dev V:39, I:68 11152 mtrace(1): malloc debugging functionality in glibc
valgrind V:1.2, I:6 129599 memory debugger and profiler
kmtrace V:0.19, I:1.7 324 KDE memory leak tracer using glibc's mtrace(1)
alleyoop V:0.06, I:0.4 1516 GNOME front-end to the Valgrind memory checker
electric-fence V:0.06, I:0.9 108 malloc(3) debugger
ccmalloc V:0.05, I:0.4 232 memory profiler/debugger
leaktracer V:0.01, I:0.13 116 memory-leak tracer for C++ programs
libdmalloc5 V:0.02, I:0.13 356 debug memory allocation library
mpatrolc2 V:0.00, I:0.03 3592 library for debugging memory allocations

12.3.5. Disassemble binary

You can disassemble binary code with objdump(1). For example:

$  objdump -m i386 -b binary -D /usr/lib/grub/x86_64-pc/stage1
[注意] 注意

gdb(1) may be used to disassemble code interactively.

12.3.6. Flex — a better Lex

Flex is a a Lex-compatible fast lexical analyzer generator.

Tutorial for flex(1) can be found in "info flex".

You need to provide your own "main()" and "yywrap()", or your "program.l" should look like this to compile without a library ("yywrap" is a macro; "%option main" turns on "%option noyywrap" implicitly):

%option main
%%
.|\n    ECHO ;
%%

Alternatively, you may compile with the "-lfl" linker option at the end of your cc(1) command line (like AT&T-Lex with "-ll"). No "%option" is needed in this case.

12.3.7. Bison — a better Yacc

Several packages provide a Yacc-compatible lookahead LR parser or LALR parser generator in Debian:

表12.13 List of Yacc-compatible LALR parser generators

パッケージ popcon サイズ 説明
bison V:2, I:17 1820 GNU LALR parser generator
byacc V:0.15, I:1.2 160 The Berkeley LALR parser generator
btyacc V:0.00, I:0.06 248 Backtracking parser generator based on byacc

Tutorial for bison(1) can be found in "info bison".

You need to provide your own "main()" and "yyerror()". "main()" calls "yyparse()" which calls "yylex()", usually created with Flex.

%%

%%

12.4. Autoconf

Autoconf is a tool for producing shell scripts that automatically configure software source code packages to adapt to many kinds of Unix-like systems using the entire GNU build system.

autoconf(1) produces the configuration script "configure". "configure" automatically creates a customized "Makefile" using the "Makefile.in" template.

12.4.1. Compile and install a program

[警告] 警告

Do not overwrite system files with your compiled programs when installing them.

Debian does not touch files in "/usr/local/" or "/opt". So if you compile a program from source, install it into "/usr/local/" so it will not interfere with Debian.

$ cd src
$ ./configure --prefix=/usr/local
$ make
$ make install # this puts the files in the system

12.4.2. Uninstall program

If you still have the source and if it uses autoconf(1)/automake(1) and if you can remember how you configured it:

$ ./configure ''all-of-the-options-you-gave-it''
# make uninstall

Alternatively, if you are absolutely sure that the install process puts files only under "/usr/local/" and there is nothing important there, you can erase all its contents by:

# find /usr/local -type f -print0 | xargs -0 rm -f

If you are not sure where files are installed, you should consider using checkinstall(8) from the checkinstall package, which provides a clean path for the uninstall. It now supports to create a Debian package with "-D" option.

12.5. Perl short script madness

Although any AWK scripts can be automatically rewritten in Perl using a2p(1), one-liner AWK scripts are best converted to one-liner perl scripts manually. For example

awk '($2=="1957") { print $3 }' |

is equivalent to any one of the following lines:

perl -ne '@f=split; if ($f[1] eq "1957") { print "$f[2]\n"}' |
perl -ne 'if ((@f=split)[1] eq "1957") { print "$f[2]\n"}' |
perl -ne '@f=split; print $f[2] if ( $f[1]==1957 )' |
perl -lane 'print $F[2] if $F[1] eq "1957"' |
perl -lane 'print$F[2]if$F[1]eq+1957' |

The last one is a riddle. It took advantage of the Perl features that

  • the whitespace is optional and
  • the automatic conversion from number to the string. See perlrun(1) for the command-line options. For more crazy Perl scripts, Perl Golf may be interesting.

12.6. Web

Basic interactive dynamic web pages can be made as follows:

  • Queries are presented to the browser user using HTML forms.
  • Filling and clicking on the form entries will send an URL with encoded parameters from the browser to the web server. For example:

    • "http://www.foo.dom/cgi-bin/program.pl?VAR1=VAL1&VAR2=VAL2&VAR3=VAL3"
    • "http://www.foo.dom/cgi-bin/program.py?VAR1=VAL1&VAR2=VAL2&VAR3=VAL3"
    • "http://www.foo.dom/program.php?VAR1=VAL1&VAR2=VAL2&VAR3=VAL3"
  • "%nn" in URL is replaced with a character with hexadecimal nn value.
  • The environment variable is set as: "QUERY_STRING="VAR1=VAL1 VAR2=VAL2 VAR3=VAL3""
  • CGI program (any one of "program.*") on the web server executes itself with the environment variable "$QUERY_STRING".
  • stdout of CGI program will be sent to the web browser and is presented as an interactive dynamic web page.

For security reasons it is better not to hand craft new hacks for parsing CGI parameters. There are established modules for them in Perl and Python. PHP comes with these functionalities. When client data storage is needed, cookies are used. When client side data processing is needed, javascript is frequently used.

For more, see The Common Gateway Interface, The Apache Software Foundation, and JavaScript.

Searching "CGI tutorial" on Google by typing encoded URL http://www.google.com/search?hl=en&ie=UTF-8&q=CGI+tutorial directly to the browser address is a good way to see the CGI script in action on the Google server.

12.7. Static code analysis tools

There are lint like tools for static code analysis:

表12.14 静的コード分析ツールのリスト。

パッケージ popcon サイズ 説明
splint V:0.06, I:0.5 1836 A tool for statically checking C programs for bugs
rats V:0.06, I:0.2 768 Rough Auditing Tool for Security (C, C++, PHP, Perl, and Python code)
flawfinder V:0.03, I:0.2 192 A tool to examine C/C++ source code and looks for security weaknesses
perl V:89, I:99 18824 This package has internal code static checker: B::Lint(3perl)
pylint V:0.10, I:0.5 688 A python code static checker
jlint V:0.01, I:0.10 184 A Java program checker
weblint-perl V:0.14, I:0.8 64 A syntax and minimal style checker for HTML
linklint V:0.06, I:0.3 432 A fast link checker and web site maintenance tool
libxml2-utils V:5, I:53 120 This package provides xmllint(1) to validate XML files

12.8. ソースコード変換

ソースコード変換するプログラムがあります。

表12.15 ソースコードの変換ツールのリスト。

パッケージ popcon サイズ keyword 説明
perl V:89, I:99 18824 AWK→PERL a2p(1) converts source codes from AWK to PERL.
f2c V:0.17, I:1.1 440 FORTRAN→C f2c(1) converts source codes from A FORTRAN 77 to C/C++.
protoize V:0.01, I:0.07 172 ANSI C Create/remove ANSI prototypes from C code.
intel2gas V:0.01, I:0.08 344 intel→gas The converter from NASM (intel format) to the GNU Assembler (GAS).

12.9. Debianパッケージ作成

Debianパッケージを作りたい場合には、次を読みましょう:

dh-makedh-make-perl等のようなパッケージングを補助するパッケージもあります。