Syntax Help | unix | grep | regular expression

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Top Forums UNIX for Dummies Questions & Answers Syntax Help | unix | grep | regular expression | repetition Post 302360954 by MykC on Sunday 11th of October 2009 04:43:57 PM

10-11-2009

Registered User

Syntax Help | unix | grep | regular expression | repetition

Hello,

This is my first post so, Hello World! Anyways, I'm learning how to use unix and its quickly become apparent that a strong foundation in regular expressions will make things easier. I'm not sure if my syntax is messing things up or my logic is messing things up.

Code:

ps -e | grep '\b[1-9][0-9]\{3,}\b'

So, I want a list of most of the current processes ps -e generates a list similar to the one below but with more lines.

Quote:

5429 tty1 00:00:00 agetty
5430 tty2 00:00:00 agetty
5431 tty3 00:00:00 agetty
5432 tty4 00:00:00 agetty
5433 tty5 00:00:00 agetty
5434 tty6 00:00:00 agetty
9266 ? 00:00:04 smbd
9578 ? 00:00:00 screen
9579 pts/2 00:01:22 rtorrent
12447 ? 00:00:00 sshd
12451 ? 00:00:00 sshd
12452 pts/0 00:00:00 bash
16109 ? 00:00:00 sshd
16112 ? 00:00:00 sshd
16113 pts/1 00:00:00 bash
16118 pts/1 00:00:00 ps

Pattern: I want to reduce the output to only include lines that have numbers greater than 1000.
Program: I'll use grep to print the lines matching the above pattern.
Options: I don't think I need to use any options.
Regular Expression: \b[1-9][0-9]\{3,}\b
File: ps -e (omitted)

Again the fully command line argument(?correct term) is:

Code:

ps -e | grep '\b[1-9][0-9]\{3,}\b'

I read the regular expression as:
\b: Check for world boundary before the string.
[1-9]: The first character in the string must be between 1 and 9.
[0-9]: The second character in the string must be between 0 and 9.
\{3,}: Replaces the above statement with: The characters following the first match must match between 0 and 9 at least 3 more times.
Kinda would look like \b[1-9][0-9][0-9][0-9]\b (for the min)
\bCheck for word boundary at the end of the string.

The return I get is:

Quote:

grep: Unmatched \{

I'm probably missing something simple but I can't figure it out.

The repetition code was taken from http://www.regular-expressions.info/repeat.html and altered a bit to apply to a use that I could create.
I also referenced the grep - Linux Command - Unix Command for info on grep.

MykC

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LEARN ABOUT OPENSOLARIS

re_comp

re_comp(3C)						   Standard C Library Functions 					       re_comp(3C)

NAME

       re_comp, re_exec - compile and execute regular expressions

SYNOPSIS

       #include <re_comp.h>

       char *re_comp(const char *string);

       int re_exec(const char *string);

DESCRIPTION

       The  re_comp() function converts a regular expression string (RE) into an internal form suitable for pattern matching.  The re_exec() func-
       tion compares the string pointed to by the string argument with the last regular expression passed to re_comp().

       If re_comp() is called with a null pointer argument, the current regular expression remains unchanged.

       Strings passed to both re_comp() and re_exec() must be terminated by a null byte, and may include NEWLINE characters.

       The re_comp() and re_exec() functions support simple regular expressions, which are defined on the  regexp(5)  manual  page.  The   regular
       expressions of the form {m}, {m,}, or {m,n} are not supported.

RETURN VALUES

       The  re_comp()  function  returns a null pointer when the string pointed to by the string argument is successfully converted.  Otherwise, a
       pointer to one of the following error message strings is returned:

	 No previous regular expression
	 Regular expression too long
	 unmatched (
	 missing ]
	 too many () pairs
	 unmatched )

       Upon successful completion, re_exec() returns 1 if string matches the last compiled regular expression.	Otherwise, re_exec() returns 0	if
       string  fails  to  match the last compiled regular expression, and -1 if the compiled regular expression is invalid (indicating an internal
       error).

ERRORS

       No errors are defined.

USAGE

       For portability to implementations conforming to X/Open standards prior to SUS, regcomp(3C) and regexec(3C) are preferred  to  these  func-
       tions.  See standards(5).

SEE ALSO

       grep(1), regcmp(1), regcmp(3C), regcomp(3C), regexec(3C), regexpr(3GEN), regexp(5), standards(5)

SunOS 5.11							    26 Feb 1997 						       re_comp(3C)