Question

claProductVersion=`head -l ${amSqlCre}` 
claProductVersion=`expr "${claProductVersion}" : 'Create Table \([^ ]*\) ('`

1. Why we are using “:” here ?
2. What ([^ ]*) is doing ?
3. What does head -l doing ? As I did not find any “l” option in head man pages.

Answer 1

1 man expr will tell you STRING : REGEXP and this means anchored pattern match of REGEXP in STRING

2 The regexp \([^ ]*\) will match strings like xxx. [^ ] means any character except whitespace. And * means repeat any times including zero. The \( and \) means showing the string matched. Without them, the result will the position the regexp matched.

3 Still I guess there’s something wrong. l doesn’t make sense here. It should be a 1.