このページではエディタとコマンドライン端末を使います。(端末から操作)と書いておきました。その欄のうち入力するのは $ が最初にある行だけです。端末の $ で終わっている行にテキストの $ 文字の後の部分を入力し、[Enter]キーを押すことでコンピュータから反応があります。詳しくは次の別ページの解説を見てください。
有名なCのプログラム例を実際にコンパイルしてみます。まずはソースファイルを作ります。次のプログラムを書いてHello.cという名前で保存します。
#include <stdio.h> int main(void) { printf("Hello, World!\n"); return 0; }
コンパイルします。
$ gcc Hello.c -o Hello
Helloという名前のファイルができています。
$ ls -l -rwx------ 1 hoge hoge 6273 2009-05-06 20:00 Hello -rw------- 1 hoge hoge 82 2009-05-06 20:00 Hello.c
実行します。
$ ./Hello Hello, World!
この時実行されるのはHello.cではなくコンパイルして作成されたHelloです。
Hello.cを調べます。fileというコマンドで調べることができます。
$ file Hello.c Hello.c: ASCII C program text
ASCIIで書かれたテキストファイルでCのプログラムだといっています。
テキストはcatコマンドで内容を表示できます。
$ cat Hello.c #include <stdio.h> int main(void) { printf("Hello, World!\n"); return 0; }
ではコンパイルの結果作成されたHelloは
$ file Hello Hello: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.8, not stripped
このファィルはcatコマンドで表示するとまともに読めません。odコマンドでコードを見ることができます。
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04 00 00 00 04 00 00 00 28 01 00 00 28 81 04 08 >........(...(...< 0000340 28 81 04 08 20 00 00 00 20 00 00 00 04 00 00 00 >(... ... .......< 0000360 04 00 00 00 51 e5 74 64 00 00 00 00 00 00 00 00 >....Q.td........< 0000400 00 00 00 00 00 00 00 00 00 00 00 00 06 00 00 00 >................< 0000420 04 00 00 00 2f 6c 69 62 2f 6c 64 2d 6c 69 6e 75 >..../lib/ld-linu< 0000440 78 2e 73 6f 2e 32 00 00 04 00 00 00 10 00 00 00 >x.so.2..........< 0000460 01 00 00 00 47 4e 55 00 00 00 00 00 02 00 00 00 >....GNU.........< 0000500 06 00 00 00 08 00 00 00 03 00 00 00 05 00 00 00 >................< 0000520 01 00 00 00 03 00 00 00 04 00 00 00 00 00 00 00 >................< 0000540 00 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00 >................< 0000560 02 00 00 00 04 00 00 00 01 00 00 00 05 00 00 00 >................< 0000600 00 20 00 20 00 00 00 00 04 00 00 00 ad 4b e3 c0 >. . .........K..< 0000620 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< 0000640 01 00 00 00 00 00 00 00 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00 00 54 82 04 08 00 00 00 00 >........T.......< 0011160 03 00 09 00 00 00 00 00 5c 82 04 08 00 00 00 00 >........\.......< 0011200 03 00 0a 00 00 00 00 00 74 82 04 08 00 00 00 00 >........t.......< 0011220 03 00 0b 00 00 00 00 00 a4 82 04 08 00 00 00 00 >................< 0011240 03 00 0c 00 00 00 00 00 f0 82 04 08 00 00 00 00 >................< 0011260 03 00 0d 00 00 00 00 00 6c 84 04 08 00 00 00 00 >........l.......< 0011300 03 00 0e 00 00 00 00 00 88 84 04 08 00 00 00 00 >................< 0011320 03 00 0f 00 00 00 00 00 a0 84 04 08 00 00 00 00 >................< 0011340 03 00 10 00 00 00 00 00 a4 94 04 08 00 00 00 00 >................< 0011360 03 00 11 00 00 00 00 00 ac 94 04 08 00 00 00 00 >................< 0011400 03 00 12 00 00 00 00 00 b4 94 04 08 00 00 00 00 >................< 0011420 03 00 13 00 00 00 00 00 b8 94 04 08 00 00 00 00 >................< 0011440 03 00 14 00 00 00 00 00 88 95 04 08 00 00 00 00 >................< 0011460 03 00 15 00 00 00 00 00 8c 95 04 08 00 00 00 00 >................< 0011500 03 00 16 00 00 00 00 00 a4 95 04 08 00 00 00 00 >................< 0011520 03 00 17 00 00 00 00 00 ac 95 04 08 00 00 00 00 >................< 0011540 03 00 18 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< 0011560 03 00 19 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< 0011600 03 00 1a 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< 0011620 03 00 1b 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< 0011640 03 00 1c 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< 0011660 03 00 1d 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< 0011700 03 00 1e 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< 0011720 03 00 1f 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< 0011740 03 00 20 00 01 00 00 00 00 00 00 00 00 00 00 00 >.. .............< 0011760 04 00 f1 ff 08 00 00 00 00 00 00 00 00 00 00 00 >................< 0012000 04 00 f1 ff 13 00 00 00 00 00 00 00 00 00 00 00 >................< 0012020 04 00 f1 ff 1e 00 00 00 a4 94 04 08 00 00 00 00 >................< 0012040 01 00 11 00 2c 00 00 00 ac 94 04 08 00 00 00 00 >....,...........< 0012060 01 00 12 00 3a 00 00 00 b4 94 04 08 00 00 00 00 >....:...........< 0012100 01 00 13 00 47 00 00 00 20 83 04 08 00 00 00 00 >....G... .......< 0012120 02 00 0d 00 5d 00 00 00 ac 95 04 08 01 00 00 00 >....]...........< 0012140 01 00 18 00 6c 00 00 00 b0 95 04 08 04 00 00 00 >....l...........< 0012160 01 00 18 00 7a 00 00 00 80 83 04 08 00 00 00 00 >....z...........< 0012200 02 00 0d 00 13 00 00 00 00 00 00 00 00 00 00 00 >................< 0012220 04 00 f1 ff 86 00 00 00 a8 94 04 08 00 00 00 00 >................< 0012240 01 00 11 00 93 00 00 00 a0 84 04 08 00 00 00 00 >................< 0012260 01 00 10 00 a1 00 00 00 b4 94 04 08 00 00 00 00 >................< 0012300 01 00 13 00 ad 00 00 00 40 84 04 08 00 00 00 00 >........@.......< 0012320 02 00 0d 00 08 00 00 00 00 00 00 00 00 00 00 00 >................< 0012340 04 00 f1 ff c3 00 00 00 00 00 00 00 00 00 00 00 >................< 0012360 04 00 f1 ff cb 00 00 00 8c 95 04 08 00 00 00 00 >................< 0012400 01 02 16 00 e1 00 00 00 a4 94 04 08 00 00 00 00 >................< 0012420 00 02 11 00 f2 00 00 00 a4 94 04 08 00 00 00 00 >................< 0012440 00 02 11 00 05 01 00 00 b8 94 04 08 00 00 00 00 >................< 0012460 01 02 14 00 0e 01 00 00 a4 95 04 08 00 00 00 00 >................< 0012500 20 00 17 00 19 01 00 00 d0 83 04 08 05 00 00 00 > ...............< 0012520 12 00 0d 00 29 01 00 00 f0 82 04 08 00 00 00 00 >....)...........< 0012540 12 00 0d 00 30 01 00 00 00 00 00 00 00 00 00 00 >....0...........< 0012560 20 00 00 00 3f 01 00 00 00 00 00 00 00 00 00 00 > ...?...........< 0012600 20 00 00 00 53 01 00 00 88 84 04 08 04 00 00 00 > ...S...........< 0012620 11 00 0f 00 5a 01 00 00 6c 84 04 08 00 00 00 00 >....Z...l.......< 0012640 12 00 0e 00 60 01 00 00 00 00 00 00 b9 01 00 00 >....`...........< 0012660 12 00 00 00 7d 01 00 00 8c 84 04 08 04 00 00 00 >....}...........< 0012700 11 00 0f 00 8c 01 00 00 a4 95 04 08 00 00 00 00 >................< 0012720 10 00 17 00 99 01 00 00 a8 95 04 08 00 00 00 00 >................< 0012740 11 02 17 00 a6 01 00 00 b0 94 04 08 00 00 00 00 >................< 0012760 11 02 12 00 b3 01 00 00 e0 83 04 08 5a 00 00 00 >............Z...< 0013000 12 00 0d 00 c3 01 00 00 ac 95 04 08 00 00 00 00 >................< 0013020 10 00 f1 ff cf 01 00 00 b4 95 04 08 00 00 00 00 >................< 0013040 10 00 f1 ff d4 01 00 00 00 00 00 00 cc 01 00 00 >................< 0013060 12 00 00 00 e4 01 00 00 ac 95 04 08 00 00 00 00 >................< 0013100 10 00 f1 ff eb 01 00 00 3a 84 04 08 00 00 00 00 >........:.......< 0013120 12 02 0d 00 02 02 00 00 a4 83 04 08 2b 00 00 00 >............+...< 0013140 12 00 0d 00 07 02 00 00 74 82 04 08 00 00 00 00 >........t.......< 0013160 12 00 0b 00 00 69 6e 69 74 2e 63 00 69 6e 69 74 >.....init.c.init< 0013200 66 69 6e 69 2e 63 00 63 72 74 73 74 75 66 66 2e >fini.c.crtstuff.< 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5f 5f 69 6e 69 74 5f 61 72 72 >y_end.__init_arr< 0013560 61 79 5f 73 74 61 72 74 00 5f 44 59 4e 41 4d 49 >ay_start._DYNAMI< 0013600 43 00 64 61 74 61 5f 73 74 61 72 74 00 5f 5f 6c >C.data_start.__l< 0013620 69 62 63 5f 63 73 75 5f 66 69 6e 69 00 5f 73 74 >ibc_csu_fini._st< 0013640 61 72 74 00 5f 5f 67 6d 6f 6e 5f 73 74 61 72 74 >art.__gmon_start< 0013660 5f 5f 00 5f 4a 76 5f 52 65 67 69 73 74 65 72 43 >__._Jv_RegisterC< 0013700 6c 61 73 73 65 73 00 5f 66 70 5f 68 77 00 5f 66 >lasses._fp_hw._f< 0013720 69 6e 69 00 5f 5f 6c 69 62 63 5f 73 74 61 72 74 >ini.__libc_start< 0013740 5f 6d 61 69 6e 40 40 47 4c 49 42 43 5f 32 2e 30 >_main@@GLIBC_2.0< 0013760 00 5f 49 4f 5f 73 74 64 69 6e 5f 75 73 65 64 00 >._IO_stdin_used.< 0014000 5f 5f 64 61 74 61 5f 73 74 61 72 74 00 5f 5f 64 >__data_start.__d< 0014020 73 6f 5f 68 61 6e 64 6c 65 00 5f 5f 44 54 4f 52 >so_handle.__DTOR< 0014040 5f 45 4e 44 5f 5f 00 5f 5f 6c 69 62 63 5f 63 73 >_END__.__libc_cs< 0014060 75 5f 69 6e 69 74 00 5f 5f 62 73 73 5f 73 74 61 >u_init.__bss_sta< 0014100 72 74 00 5f 65 6e 64 00 70 75 74 73 40 40 47 4c >rt._end.puts@@GL< 0014120 49 42 43 5f 32 2e 30 00 5f 65 64 61 74 61 00 5f >IBC_2.0._edata._< 0014140 5f 69 36 38 36 2e 67 65 74 5f 70 63 5f 74 68 75 >_i686.get_pc_thu< 0014160 6e 6b 2e 62 78 00 6d 61 69 6e 00 5f 69 6e 69 74 >nk.bx.main._init< 0014200 00 >.<
コンパイルしたファイルには文字として解釈できない文字がありますから、16進数でバイト列をそのまま表示しています。右の><で挟まれたところには文字と解釈できるものはその文字を、そうでない時は"."を表示しています。
コンパイルはソースを機械語に書き直すといいますが、そう単純ではないことが分かると思います。
実行はOSがこのプログラムHelloをファイルからメモリ上にロードし、始まりの場所をセットして処理を開始させます。Hello側は作業が終わればOSに制御を戻します。これが プログラムソースにあるreturnの意味です。0 は正常に終わったことを知らせるもので、UNIX系OSの取り決めです。
perlという言語のソースを作ります。次のプログラムを書いてHellopという名前で保存します。Helloでもいいのですが、Cで作ったものと名前がかぶるので変えています。ファイルの内容はたったの1行
print "Hello World!\n";
実行します。
$ perl Hellop Hello World!
実行するのはperlというプログラムで、そのプログラムにHellopというファイルを読んで実行するように指示しているわけです。perlはインタープリタでHellopはプログラムということになります。
これも内容を調べてみます。
$ ls -l -rwx------ 1 hoge hoge 6273 2009-05-06 20:00 Hello -rw------- 1 hoge hoge 82 2009-05-06 20:00 Hello.c -rw------- 1 hoge hoge 25 2009-05-06 20:20 Hellop
ファイルの内容を問い合わせてみます
$ file Hellop Hellop: ASCII text
textとあるものはcatで内容を見ることができます。
$ cat Hellop print "Hello World!\n";
odダンプもしてみましょう
$ od -tx1z Hellop 0000000 70 72 69 6e 74 20 22 48 65 6c 6c 6f 20 57 6f 72 >print "Hello Wor< 0000020 6c 64 21 5c 6e 22 3b 0a >ld!\n";.< 0000030 $
どう見てもテキストファイルですね。
UNIX系のOSでは、この perl Hellop を Hellop だけで実行する仕組みがあります。ファイル名が「命令」のように見えるのでわかりやすくなります。
ファイルの先頭に次の1行を加えます。こんどはHelloperlという名前で保存しましょう。
#!/usr/bin/perl print "Hello World!\n";
今度は実行前にもう一つしなければならないことがあります。
$ ls -l -rwx------ 1 hoge hoge 6273 2009-05-06 20:00 Hello -rw------- 1 hoge hoge 82 2009-05-06 20:00 Hello.c -rw------- 1 hoge hoge 40 2009-05-06 20:24 Helloperl -rw------- 1 hoge hoge 25 2009-05-06 20:20 Hellop
このファイルのrw-------の部分はパーミッションといって、このファイルの持ち主が読む権限(r)と書く権限(w)を持っていることを表しています。これに実行する権限(x)を加えなければ実行できません。
$ chmod u+x Helloperl
u+xが持ち主(user)に実行権限(x)を加えるという意味です。
実行権限(x)が加えられたことを確認します。
$ ls -l -rwx------ 1 hoge hoge 6273 2009-05-06 20:00 Hello -rw------- 1 hoge hoge 82 2009-05-06 20:00 Hello.c -rwx------ 1 hoge hoge 40 2009-05-06 20:24 Helloperl -rw------- 1 hoge hoge 25 2009-05-06 20:20 Hellop
一度権限が設定されると、再設定されるまで有効になりますからこの作業は1度だけ必要です。
実行します。
$ ./Helloperl Hello World!
ファイルの内容を問い合わせてみます
$ file Helloperl Helloperl: a /usr/bin/perl script text executable
今度はperlのスクリプト(プログラム)でテキストで書かれていて、実行可能であると言っています。
後は同じです。textとあるものはcatで内容を見ることができます。
$ cat Helloperl #!/usr/bin/perl print "Hello World!\n";
odダンプもしてみましょう
$ od -tx1z Helloperl 0000000 23 21 2f 75 73 72 2f 62 69 6e 2f 70 65 72 6c 0a >#!/usr/bin/perl.< 0000020 70 72 69 6e 74 20 22 48 65 6c 6c 6f 20 57 6f 72 >print "Hello Wor< 0000040 6c 64 21 5c 6e 22 3b 0a >ld!\n";.<
端末の中で私たちのコマンドラインからの命令を解釈して実行しているプログラムをシェル(shell)と言います。シェルにはコマンドをあらかじめファイルに書いておいてまとめて実行するという仕組みがあります。これをシェルスクリプトといいます。
これもインタープリタ型の言語といえます
ソースを作ります。次のプログラムを書いてHellosという名前で保存します。もちろんこれもHelloでもいいのですが、Cで作ったものと名前がかぶるので変えています。ファイルの内容はたったの1行
echo "Hello World!\n"
そして実行権は、
$ sh Hellos Hello World!\n
または、
$ . Hellos Hello World!\n
実行権があればファイル名だけで実行できます。
$ chmod u+x Hellos $ ./Hellos Hello World!\n
perlでは1行目に何というインタプリタで実行するかを指定しましたが、これを書かなければいつも使っているシェルで実行されます。もし書きたければ、
#!/bin/sh echo "Hello World!\n"
とします。
実は先頭の#!でインタープリタを指定する仕組みが作られたのは、シェルにいくつかの種類があって、若干書き方が異なったからです。シーエルはユーザーの好みで切り替えられるのですが、だれが実行しても同じシェルで実行するようにしなければならなかったのでした。ついでに、perl, python, rubyなど将来作成される物も含めていろいろなインタープリタを指定してプログラムをコマンドのように実行できるようにしました。これはすごくステキな仕組みです。
ちなみにLinuxの多くがbashというシェルを標準としています。他に、csh や tch などがありますが、標準のシェルは sh という別名を付けるのが普通です。
聖愛中学高等学校