PASMO の設定変更完了。
新しいタイプの券売機だととても楽だった
(でなければ定期券売り場の窓口に行ってごにょごにょ…だったらしい)
なぜマニュアルを見ないのだろう…
Bashの括弧 - 超ウィザード級ハッカーのたのしみ
で、調べてみたら結構バラバラで探すのに苦労したw
(少なくとも、索引からすぐ。というわけにはいかなかった)
Bash Reference Manual
3.5.1 Brace Expansion
Bash Reference Manual
3.2.4.2 Conditional Constructs
(略)
((…))
(( expression ))
The arithmetic expression is evaluated according to the rules described below (see Shell Arithmetic).
If the value of the expression is non-zero, the return status is 0; otherwise the return status is 1.
This is exactly equivalent to
let "expression"
See Bash Builtins, for a full description of the let builtin.
[[…]]
[[ expression ]]
Return a status of 0 or 1 depending on the evaluation of the conditional expression expression.
Expressions are composed of the primaries described below in Bash Conditional Expressions.
Word splitting and filename expansion are not performed on the words between the [[ and ]];
tilde expansion, parameter and variable expansion, arithmetic expansion, command substitution,
process substitution, and quote removal are performed. Conditional operators such as ‘-f’ must be
unquoted to be recognized as primaries.
Bash Reference Manual
3.2.4.3 Grouping Commands
Bash provides two ways to group a list of commands to be executed as a unit. When commands are grouped,
redirections may be applied to the entire command list. For example, the output of all the commands
in the list may be redirected to a single stream.
()
( list )
Placing a list of commands between parentheses causes a subshell environment to be created (see Command
Execution Environment), and each of the commands in list to be executed in that subshell. Since the list is
executed in a subshell, variable assignments do not remain in effect after the subshell completes.
{}
{ list; }
Placing a list of commands between curly braces causes the list to be executed in the current shell context.
No subshell is created. The semicolon (or newline) following list is required.
In addition to the creation of a subshell, there is a subtle difference between these two constructs due to
historical reasons. The braces are reserved words, so they must be separated from the list by blanks
or other shell metacharacters. The parentheses are operators, and are recognized as separate tokens by
the shell even if they are not separated from the list by whitespace.
The exit status of both of these constructs is the exit status of list.
Bash Reference Manual
3.5.3 Shell Parameter Expansion
The ‘$’ character introduces parameter expansion, command substitution, or arithmetic expansion. The parameter
name or symbol to be expanded may be enclosed in braces, which are optional but serve to protect the variable
to be expanded from characters immediately following it which could be interpreted as part of the name.
When braces are used, the matching ending brace is the first ‘}’ not escaped by a backslash or within
a quoted string, and not within an embedded arithmetic expansion, command substitution, or parameter expansion.
The basic form of parameter expansion is ${parameter}. The value of parameter is substituted. The parameter is a
shell parameter as described above (see Shell Parameters) or an array reference (see Arrays).
The braces are required when parameter is a positional parameter with more than one digit,
or when parameter is followed by a character that is not to be interpreted as part of its name.
Bash Reference Manual
3.5.4 Command Substitution
Command substitution allows the output of a command to replace the command itself. Command substitution occurs
when a command is enclosed as follows:
$(command)
or
`command`
Bash performs the expansion by executing command and replacing the command substitution with the standard output
of the command, with any trailing newlines deleted. Embedded newlines are not deleted, but they may be
removed during word splitting. The command substitution $(cat file) can be replaced by the equivalent
but faster $(< file).
以下略
Bash Reference Manual
3.5.5 Arithmetic Expansion
Arithmetic expansion allows the evaluation of an arithmetic expression and the substitution of the result.
The format for arithmetic expansion is:
$(( expression ))
The expression is treated as if it were within double quotes, but a double quote inside the parentheses is not
treated specially. All tokens in the expression undergo parameter and variable expansion, command substitution,
and quote removal. The result is treated as the arithmetic expression to be evaluated.
Arithmetic expansions may be nested.
The evaluation is performed according to the rules listed below (see Shell Arithmetic). If the expression is
invalid, Bash prints a message indicating failure to the standard error and no substitution occurs.
Bash Reference Manual
3.5.6 Process Substitution
Process substitution is supported on systems that support named pipes (FIFOs) or the /dev/fd method of
naming open files. It takes the form of
<(list)
or
>(list)
The process list is run with its input or output connected to a FIFO or some file in /dev/fd.
The name of this file is passed as an argument to the current command as the result of the expansion.
If the >(list) form is used, writing to the file will provide input for list.
If the <(list) form is used, the file passed as an argument should be read to obtain the output of list.
Note that no space may appear between the < or > and the left parenthesis, otherwise the construct
would be interpreted as a redirection.
When available, process substitution is performed simultaneously with parameter and variable expansion,
command substitution, and arithmetic expansion.
Bash Reference Manual
6.7 Arrays
(略)
Arrays are assigned to using compound assignments of the form
name=(value1 value2 … )
sedの-iオプションの非互換 - Qiita
これ、「シェル」じゃなくてgetopt(とgetopt_long)の仕様の違いじゃないのかね。
訳がちとあれだけど日本語のやつで。
GETOPT(3) - 標準Cライブラリ関数 - YOS OPENSONAR
GETOPT(3) - サブルーチン - YOS OPENSONAR
getopt() 関数は、コマンドラインの引数リスト argv を増加させながら解析して、次の 既知 オプション文字を返します。
受け入れオプション文字集合 optstring に指定されていた場合、そのオプション文字は、 既知 です。
オプション文字列 optstring は、次の要素を含めます。個々の文字と、
後にオプションの引数が続くことを意味する後にコロンが付いた文字です。
例えば、オプション文字列 "x" は、オプション“ -x”と認識され、オプション文字列 "x:" は、
オプションと引数“ -x argument”と認識されます。後に続く引数に先導する空白があっても、
getopt() には重要ではありません。
getopt() から戻った時、 optarg は、それが予期されていればオプションの引数を指しており、変数 optind は、
続く getopt() 呼び出しのための argv 引数のインデックスが含まれます。変数 optopt は、
getopt() によって返された最後の 既知 オプション文字を保存してます。
BSD はこうだけど
Man page of GETOPT
struct option {
const char *name;
int has_arg;
int *flag;
int val;
};
それぞれのフィールドの意味は以下の通り。
name
長いオプションの名前。
has_arg
no_argument (または 0) なら、オプションは引き数をとらない。 required_argument (または 1) なら、
オプションは引き数を必要とする。 optional_argument (または 2) なら、
オプションは引き数をとっても とらなくても良い。
で、実際 GNU sed では
#define COPYRIGHT_NOTICE "Copyright (C) 2003 Free Software Foundation, Inc."
/* GNU SED, a batch stream editor.
Copyright (C) 1989,90,91,92,93,94,95,98,99,2002,2003
Free Software Foundation, Inc.
(略)
int
main(argc, argv)
int argc;
char **argv;
{
#ifdef REG_PERL
#define SHORTOPTS "bsnrRuEe:f:l:i::V:"
#else
#define SHORTOPTS "bsnruEe:f:l:i::V:"
#endif
static struct option longopts[] = {
{"binary", 0, NULL, 'b'},
{"regexp-extended", 0, NULL, 'r'},
#ifdef REG_PERL
{"regexp-perl", 0, NULL, 'R'},
#endif
{"expression", 1, NULL, 'e'},
{"file", 1, NULL, 'f'},
{"in-place", 2, NULL, 'i'},
{"line-length", 1, NULL, 'l'},
{"quiet", 0, NULL, 'n'},
{"posix", 0, NULL, 'p'},
{"silent", 0, NULL, 'n'},
{"separate", 0, NULL, 's'},
{"unbuffered", 0, NULL, 'u'},
{"version", 0, NULL, 'v'},
{"help", 0, NULL, 'h'},
#ifdef ENABLE_FOLLOW_SYMLINKS
{"follow-symlinks", 0, NULL, 'F'},
#endif
{NULL, 0, NULL, 0}
};
(略)
while ((opt = getopt_long(argc, argv, SHORTOPTS, longopts, NULL)) != EOF)
{
switch (opt)
{
(略)
case 'i':
separate_files = true;
if (optarg == NULL)
/* use no backups */
in_place_extension = ck_strdup ("*");
else if (strchr(optarg, '*') != NULL)
in_place_extension = ck_strdup(optarg);
else
{
in_place_extension = MALLOC (strlen(optarg) + 2, char);
in_place_extension[0] = '*';
strcpy (in_place_extension + 1, optarg);
}
break;
(オプションに対する引数が)省略可能な指定になってて、
オプション解析の部分でも optarg == NULL で引数があるか判定して切り分けてる。
おまけ。
$ cat >foo.sh
echo $1
echo $2
$ bash foo.sh aaa bbb
aaa
bbb
$ bash foo.sh '' aaa bbb
aaa
$ bash foo.sh ''aaa bbb
aaa
bbb
