Pig大的运行方法：
1、脚本
2、Grunt
3、嵌入式
Grunt
1、自动补全机制 （命令补全、不支持文件名补全）
2、autocomplete文件
3、Eclipse插件PigPen
进入Grunt shell命令
[hadoop@master pig]$ ./bin/pig
2013-04-13 23:00:19,909 [main] INFO org.apache.pig.Main - Apache Pig version 0.10.0 (r1328203) compiled Apr 19 2012, 22:54:12
2013-04-13 23:00:19,909 [main] INFO org.apache.pig.Main - Logging error messages to: /opt/pig/pig_1365865219902.log
2013-04-13 23:00:20,237 [main] INFO org.apache.pig.backend.hadoop.executionengine.HExecutionEngine - Connecting to hadoop file system at: hdfs://192.168.154.100:9000
2013-04-13 23:00:20,536 [main] INFO org.apache.pig.backend.hadoop.executionengine.HExecutionEngine - Connecting to map-reduce job tracker at: 192.168.154.100:9001
帮助（help）
grunt> help
Commands:
<pig latin statement>; - See the PigLatin manual for details: http://hadoop.apache.org/pig
File system commands:
fs <fs arguments> - Equivalent to Hadoop dfs command: http://hadoop.apache.org/common/docs/current/hdfs_shell.html
Diagnostic commands:
describe <alias>[::<alias] - Show the schema for the alias. Inner aliases can be described as A::B.
explain [-script <pigscript>] [-out <path>] [-brief] [-dot] [-param <param_name>=<param_value>]
[-param_file <file_name>] [<alias>] - Show the execution plan to compute the alias or for entire script.
-script - Explain the entire script.
-out - Store the output into directory rather than print to stdout.
-brief - Don't expand nested plans (presenting a smaller graph for overview).
-dot - Generate the output in .dot format. Default is text format.
-param <param_name - See parameter substitution for details.
-param_file <file_name> - See parameter substitution for details.
alias - Alias to explain.
dump <alias> - Compute the alias and writes the results to stdout.
Utility Commands:
exec [-param <param_name>=param_value] [-param_file <file_name>] <script> -
Execute the script with access to grunt environment including aliases.
-param <param_name - See parameter substitution for details.
-param_file <file_name> - See parameter substitution for details.
script - Script to be executed.
run [-param <param_name>=param_value] [-param_file <file_name>] <script> -
Execute the script with access to grunt environment.
-param <param_name - See parameter substitution for details.
-param_file <file_name> - See parameter substitution for details.
script - Script to be executed.
sh <shell command> - Invoke a shell command.
kill <job_id> - Kill the hadoop job specified by the hadoop job id.
set <key> <value> - Provide execution parameters to Pig. Keys and values are case sensitive.
The following keys are supported:
default_parallel - Script-level reduce parallelism. Basic input size heuristics used by default.
debug - Set debug on or off. Default is off.
job.name - Single-quoted name for jobs. Default is PigLatin:<script name>
job.priority - Priority for jobs. Values: very_low, low, normal, high, very_high. Default is normal
stream.skippath - String that contains the path. This is used by streaming.
any hadoop property.
help - Display this message.
quit - Quit the grunt shell.
查看（ls、cd 、cat）
grunt> ls
hdfs://192.168.154.100:9000/user/hadoop/in <dir>
hdfs://192.168.154.100:9000/user/hadoop/out <dir>
grunt> cd in
grunt> ls
hdfs://192.168.154.100:9000/user/hadoop/in/test1.txt<r 1> 12
hdfs://192.168.154.100:9000/user/hadoop/in/test2.txt<r 1> 13
hdfs://192.168.154.100:9000/user/hadoop/in/test_1.txt<r 1> 328
hdfs://192.168.154.100:9000/user/hadoop/in/test_2.txt<r 1> 139
grunt> cat test1.txt
hello world
复制到本地（copyToLocal）
grunt> ls
hdfs://192.168.154.100:9000/user/hadoop/in/test1.txt<r 1> 12
hdfs://192.168.154.100:9000/user/hadoop/in/test2.txt<r 1> 13
hdfs://192.168.154.100:9000/user/hadoop/in/test_1.txt<r 1> 328
hdfs://192.168.154.100:9000/user/hadoop/in/test_2.txt<r 1> 139
grunt> copyToLocal test1.txt ttt
[root@master pig]# ls -l ttt
-rwxrwxrwx. 1 hadoop hadoop 12 4月 13 23:06 ttt
[root@master pig]#
执行操作系统命令：sh
grunt> sh jps
2098 DataNode
1986 NameNode
2700 Jps
2539 RunJar
2297 JobTracker
2211 SecondaryNameNode
2411 TaskTracker
grunt>
Pig数据模型
Bag：表
Tuple：行，记录
Field：属性
Pig不要求同一个bag里面的各个tuple有相同数量或相同类型的field
Pig latin常用语句
LOAD：指出载入数据的方法
FOREACH：逐行扫描进行某种处理
FILTER：过滤行
DUMP：把结果显示到屏幕
STORE：把结果保存到文件
pig脚本实例：
grunt> records = LOAD 'input/ncdc/micro-tab/sample.txt'
>> AS (year:chararray, temerature:int, quality:int);
(1949,111)
(1950,22)
由此成功计算每年的最高气温。
实例二：
