getconf命令【一天一个命令】
我们时常需要查询系统相关的信息，比如页面大小，整数大小之类，如果编写程序去计算会比较繁琐，这里有一个很有用的命令，可以用来获取系统相关信息。它就是getconf。
$ getconf PAGE_SIZE
4096
$ getconf INT_MAX
2147483647
可以取得的相关信息如下(参考相关资料，在又在版本上会有些不同）：
| _CS_PATH | Value for the PATH environment variable used to find commands. |
| ARG_MAX | Maximum length, in bytes, of the arguments for one of the exec subroutines, including environment data. |
| BC_BASE_MAX | Maximum value allowed for the obase variable with the bc command. |
| BC_DIM_MAX | Maximum number of elements permitted in an array by the bc command. |
| BC_SCALE_MAX | Maximum value allowed for the scale variable with the bc command. |
| BC_STRING_MAX | Maximum length of a string constant accepted by the bc command. |
| CHARCLASS_NAME_MAX | Maximum number of bytes in a character class name. |
| CHAR_BIT | Number of bits in a type character. |
| CHAR_MAX | Maximum value of a type character. |
| CHAR_MIN | Minimum value of a type character. |
| CHILD_MAX | Maximum number of simultaneous processes for each real user ID. |
| CLK_TCK | Number of clock ticks per second returned by the time subroutine. |
| COLL_WEIGHTS_MAX | Maximum number of weights that can be assigned to an entry in the LC_COLLATE locale stanza in a locale-definition file. |
| CS_PATH | Value of the PATH environment variable used to find commands. |
| EXPR_NEST_MAX | Maximum number of expressions that can be nested within parentheses by the expr command. |
| INT_MAX | Maximum value of a type int. |
| INT_MIN | Minimum value of a type int. |
| LINE_MAX | Maximum length, in bytes, of a command's input line (either standard input or another file) when the utility is described as processing text files. The length includes room for the trailing new-line character. |
| LONG_BIT | Number of bits in a type long int. |
| LONG_MAX | Maximum value of a type long int. |
| LONG_MIN | Minimum value of a type long int. |
| MB_LEN_MAX | Maximum number of bytes in a character for any supported locale. |
| NGROUPS_MAX | Maximum number of simultaneous supplementary group IDs for each process. |
| NL_ARGMAX | Maximum value of digit in calls to the printf and scanf subroutines. |
| NL_LANGMAX | Maximum number of bytes in a LANG name. |
| NL_MSGMAX | Maximum message number. |
| NL_NMAX | Maximum number of bytes in an N-to-1 collation mapping. |
| NL_SETMAX | Maximum set number. |
| NL_TEXTMAX | Maximum number of bytes in a message string. |
| NZERO | Default process priority. |
| OPEN_MAX | Maximum number of files that one process can have open at one time. |
| PATH | Sequence of colon-separated path prefixes used to find commands. |
| RE_DUP_MAX | Maximum number of repeated occurrences of a regular expression permitted when using the interval-notation parameters, such as the m and n parameters with the ed command. |
| SCHAR_MAX | Maximum value of a type signed char. |
| SCHAR_MIN | Minimum value of a type signed char. |
| SHRT_MAX | Maximum value of a type short. |
| SHRT_MIN | Minimum value of a type short. |
| SSIZE_MAX | Maximum value of an object of type ssize_t. |
| STREAM_MAX | Number of streams that one process can have open at one time. |
| TMP_MAX | Minimum number of unique path names generated by the tmpnam subroutine. Maximum number of times an application can reliably call the tmpnam subroutine. |
| TZNAME_MAX | Maximum number of bytes supported for the name of a time zone (not the length of the TZ environment variable). |
| UCHAR_MAX | Maximum value of a type unsigned char. |
| UINT_MAX | Maximum value of a type unsigned int. |
| ULONG_MAX | Maximum value of a type unsigned long int. |
| USHRT_MAX | Maximum value of a type unsigned short int. |
| WORD_BIT | Number of bits in a word or type int |
