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Using sed in the LRPG

This document is a brief tutorial on how to use unix's sed, "stream editor" to manipulate an output list to construct a list of commands to perform on each of the visits. The example outlined below takes the output from "expire_list" which has been copied into a unix file and then uses sed to extract the sunit_ids and construct plan-window-copy commands which can be placed into a VMS com-file for batch execution.

Sed's command line syntax essentially means this:

sed 's/search_for_this/replace_with_this/' file_name_to_operate_on

Let us examine a sed command breaking it up into components to see what the individual pieces do:

sed 's/^$.......$.*$/$do copy_visit_into_lrp 98259A 98259X \1/' ~jordan/98285

sed

--invokes sed. what follows is the script which is placed inside single quotes:

's/

--sed's search and replace. What follows between the // is the expression to search for. The first "/" is the beginning of the pattern matching delimiter.

--regular expression syntax meaning "start at beginning of line".

--the "\(" is the symbol combination which means 'grab this pattern and store it'.

.......

--matches 7 characters, but in our case, since we used the "^" beginning of line anchor, it grabs the first 7 characters.

--end grab.

--any pattern length. Matches up to the . . .

--end of line!

--delimiter indicating the end of pattern matching expression. What follows to the next occurence of "/" is an expression detailing what the pattern in the first part of the grab is to be replaced with:

--this part of the sed command--the replacement string--functions differently than the first part--the search pattern. Here, the "$" sign does not mean "end of line", it means litterally "$"!

do copy_visit_into_lrp 98295A 98259X

--literally the command to executed from the vms prompt.

--replace with the first 'grabbed' expression.

--closing replacement delimiter and the "'" showing the end of the script.

~jordan/file98285

--the filename that the sed script operates on.

Examples:

sed 's/^$.......$.*$/$do copy_visit_into_lrp 98259A 98259X \1/' ~jordan/98285

Take the first 7 characters (sunit_id) from the input file ~jordan/98285 and process them into a list of VMS LRPG commands which copy them from one LRP to another.

egrep -i "Severity E" batch_log.thu | sed 's/.*$[0-9][0-9][0-9][0-9]$.*/\1c/' | sort -u

A combination command which 'greps' a batch_log file for a string containing a 4-digit proposal_id (which it grabs and stores), and then pipes it to sed so that it can grab the proposal ids and output them uniquely in a format that is compatible with find_lrp.lis input to a SPIKE run.

sed -f ~jordan/sed_script nonmama_didnt_schedule

Use of a file ~jordan/sed_script to store a sed script which is difficult to do from a command line. The script file ~jordan/sed_script contains:

s/^$.......$.*$/$cclist\/get ijj8wk \

$cand\/add \1 \

$cale\/add \1/

Note that this script outputs multiple lines instead of just one line for each input record.

More examples (uncommented) on using sed with data in files (often in conjunction with other tools):


head -1 /home/lrp/current_available_list.rpt | sed 's/.*LRP= \(.*\)/\1/'

cut -c1-7 t1204_g.available_c12_sort4 | egrep -v 9803 | sed 's/\(.......\)/(delete-pw "\1")/' > delpw

cut -c2-15 alrp | sed 's/\(.*\)/archive-lrps name=\1/' > archem