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Full Discussion: Cut too slow
Top Forums Shell Programming and Scripting Cut too slow Post 302193670 by drl on Saturday 10th of May 2008 12:57:21 PM
Old 05-10-2008
Hi.

It looks like you are processing one line at time. That will be inherently slow, because you will be loading cut for each line. Let cut process the entire file -- try to re-think your method on a file-based idea, preferably with a pipe, or, at the very least, writing an intermediate file like:
Code:
cut -c19-20 input-file >scratch-file-1

then process the scratch file ... cheers, drl
 

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CUT(1)							    BSD General Commands Manual 						    CUT(1)

NAME
cut -- cut out selected portions of each line of a file SYNOPSIS
cut -b list [-n] [file ...] cut -c list [file ...] cut -f list [-d delim] [-s] [file ...] DESCRIPTION
The cut utility cuts out selected portions of each line (as specified by list) from each file and writes them to the standard output. If no file arguments are specified, or a file argument is a single dash ('-'), cut reads from the standard input. The items specified by list can be in terms of column position or in terms of fields delimited by a special character. Column numbering starts from 1. The list option argument is a comma or whitespace separated set of numbers and/or number ranges. Number ranges consist of a number, a dash ('-'), and a second number and select the fields or columns from the first number to the second, inclusive. Numbers or number ranges may be preceded by a dash, which selects all fields or columns from 1 to the last number. Numbers or number ranges may be followed by a dash, which selects all fields or columns from the last number to the end of the line. Numbers and number ranges may be repeated, overlapping, and in any order. If a field or column is specified multiple times, it will appear only once in the output. It is not an error to select fields or columns not present in the input line. The options are as follows: -b list The list specifies byte positions. -c list The list specifies character positions. -d delim Use delim as the field delimiter character instead of the tab character. -f list The list specifies fields, separated in the input by the field delimiter character (see the -d option.) Output fields are separated by a single occurrence of the field delimiter character. -n Do not split multi-byte characters. Characters will only be output if at least one byte is selected, and, after a prefix of zero or more unselected bytes, the rest of the bytes that form the character are selected. -s Suppress lines with no field delimiter characters. Unless specified, lines with no delimiters are passed through unmodified. ENVIRONMENT
The LANG, LC_ALL and LC_CTYPE environment variables affect the execution of cut as described in environ(7). EXIT STATUS
The cut utility exits 0 on success, and >0 if an error occurs. EXAMPLES
Extract users' login names and shells from the system passwd(5) file as ``name:shell'' pairs: cut -d : -f 1,7 /etc/passwd Show the names and login times of the currently logged in users: who | cut -c 1-16,26-38 SEE ALSO
colrm(1), paste(1) STANDARDS
The cut utility conforms to IEEE Std 1003.2-1992 (``POSIX.2''). HISTORY
A cut command appeared in AT&T System III UNIX. BSD
December 21, 2006 BSD
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