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Top Forums Shell Programming and Scripting How to get a very big file sorted by contents of another variable list in one pass? Post 302459080 by methyl on Sunday 3rd of October 2010 02:40:13 PM
Old 10-03-2010
Is this a sort or a sift?
Do you need to sort the content of the 42 files? If so, what is the sort key?

Assuming no sort, sifting the main file into individual files with names based on the data characters 2-3 is relatively easy in a modern shell but it will not be quick with 17 million records.

Code:
For example:
cat filename | while read record
do
     category=`echo "${record}"|cut -c2-3`
     echo "${record}" >> "filename_${category}"
done

You can then do whatever processing you need to do in priority order.

For example:
cat reference_file | while read category
do
         ls -ald "filename_${category}"
done

 

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getusershell(3C)					   Standard C Library Functions 					  getusershell(3C)

NAME
getusershell, setusershell, endusershell - get legal user shells SYNOPSIS
#include <unistd.h> char *getusershell(void); void setusershell(void); void endusershell(void); DESCRIPTION
The getusershell() function returns a pointer to a legal user shell as defined by the system manager in the file /etc/shells. If /etc/shells does not exist, the following locations of the standard system shells are used in its place: /bin/bash /bin/csh /bin/jsh /bin/ksh /bin/pfcsh /bin/pfksh /bin/pfsh /bin/sh /bin/tcsh /bin/zsh /sbin/jsh /sbin/pfsh /sbin/sh /usr/bin/bash /usr/bin/csh /usr/bin/jsh /usr/bin/ksh /usr/bin/pfcsh /usr/bin/pfksh /usr/bin/pfsh /usr/bin/sh /usr/bin/tcsh /usr/bin/zsh /usr/xpg4/bin/sh The getusershell() function opens the file /etc/shells, if it exists, and returns the next entry in the list of shells. The setusershell() function rewinds the file or the list. The endusershell() function closes the file, frees any memory used by getusershell() and setusershell(), and rewinds the file /etc/shells. RETURN VALUES
The getusershell() function returns a null pointer on EOF. BUGS
All information is contained in memory that may be freed with a call to endusershell(), so it must be copied if it is to be saved. SunOS 5.10 30 Aug 2004 getusershell(3C)
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