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Full Discussion: sed: -e expression #1, char 0: no previous regular expression
Top Forums UNIX for Advanced & Expert Users sed: -e expression #1, char 0: no previous regular expression Post 302688727 by RudiC on Monday 20th of August 2012 04:53:00 AM
Old 08-20-2012
Quote:
Originally Posted by Don Cragun
You haven't said what shell you're using, but at least with bash and ksh, setting an array with:
Code:
array=(a b c)

sets ${array[1]} to a, ${array[2]} to b, and ${array[3]} to c. It doesn't set ${array[0]} so your first call to sed
Code:
sed  -n "/${problem_arr[0]}/,/${problem_arr[1]}/p" problemid.txt

expands to:
Code:
sed  -n "//,/PRS111/p" problemid.txt

and since your first RE is //, it is trying to search for the previously used RE (but there is no previously used RE in this invocation of sed.
Sorry, disagree. From the bash man page:
Quote:
Arrays are assigned to using compound assignments of the form name=(value1 ... valuen), where each value is of the form [sub- script]=string. Indexed array assignments do not require the bracket and subscript. When assigning to indexed arrays, if the optional brackets and subscript are supplied, that index is assigned to; other- wise the index of the element assigned is the last index assigned to by the statement plus one. Indexing starts at zero.
Running InduInduIndu's code snippet - using ${#...} to correctly get the member count - fails in the fourth loop,
Code:
++ k=4
++ sed -n //,//p problemid.txt
sed: -e expression #1, char 0: no previous regular expression

indicating that he should limit his loop count to 0 - 2. The first loop works fine:
Code:
++ sed -n /PRS111/,/PRS213/p problemid.txt

 

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LEARN ABOUT SUSE

ausearch_add_regex

AUSEARCH_ADD_REGEX(3)						  Linux Audit API					     AUSEARCH_ADD_REGEX(3)

NAME

       ausearch_add_regex - use regular expression search rule

SYNOPSIS

       #include <auparse.h>

       int ausearch_add_regex(auparse_state_t *au, const char *expr);

DESCRIPTION

       ausearch_add_regex  adds  one  search condition based on a regular expression to the current audit search expression. The search conditions
       can then be used to scan logs, files, or buffers for something of interest. The regular	expression  follows  the  posix  extended  regular
       expression conventions, and is matched against the full record (without interpreting field values).

       If an existing search expression E is already defined, this function replaces it by (E && this_regexp).

RETURN VALUE

       Returns -1 if an error occurs; otherwise, 0 for success.

SEE ALSO

       ausearch_add_expression(3), ausearch_add_item(3), ausearch_clear(3), ausearch_next_event(3), regcomp(3).

AUTHOR

       Steve Grubb

Red Hat 							     Sept 2007						     AUSEARCH_ADD_REGEX(3)
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