Rdb: Ruby-Nachbau der MWC /rdb-Werkzeuge

man/seek.man

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+.TH seek "" "" "/rdb Command"
+.PC "Return the beginning and ending offset of a row"
+\fBseek [-m[bihrs]] [-o \fIoutfile\fB] \fItableorlist \fB[\fIkeycol...\fB] < \fIfile\fR
+.PP
+.II "row^find"
+.II "row^offset"
+.II "find row"
+The command
+.B seek
+returns the offsets of the beginning and end of a record in
+.IR tableorlist .
+It uses the command
+.B search
+with its location option
+.BR \-l .
+.PP
+The offset and size integers returned can be used by the
+.B replace
+to write a new record.
+They are also used by the commands
+.B lock
+and
+.B unlock
+to set and remove record locks.
+.SH Options
+.B seek
+recognizes the following options:
+.IP \fB-m[bhirs]\fR
+Fast access methods.
+See the manual entry for the command
+.B search
+for a full description of various search options and how you can invoke each.
+.IP \fB-o\fR
+Write the found record into
+.BR outfile .
+.SH Example
+Let's use
+.B seek
+on the table
+.BR inventory ,
+which is as follows:
+.DM
+Item    Amount  Cost    Value   Description   
+----    ------  ----    -----   --------------
+   1         3    50      150   rubber gloves
+   2       100     5      500   test tubes
+   3         5    80      400   clamps
+   4        23    19      437   plates
+   5        99    24     2376   cleaning cloth
+   6        89   147    13083   bunsen burners
+   7         5   175      875   scales
+.DE
+.PP
+The following command invokes
+.B seek
+to find row 5:
+.DM
+	echo 5 | seek -mb inventory Item
+.DE
+.PP
+This writes the following to the standard output:
+.DM
+	207     245     0       8
+.DE
+.PP
+This means that the record is 207 bytes into the file and that
+it is 38 bytes long, ending at byte 245.
+.PP
+The next example
+extracts a row from
+.BR inventory
+blanks it out, then writes the row back into
+.B inventory
+on top of the original row.
+First, extract the row:
+.DM
+	LOCATION=`echo 5 | seek -mb -o tmp inventory Item`
+.DE
+.PP
+The location of the selected record is stored in environmental variable
+.BR LOCATION .
+The option
+.B "\-o tmp"
+writes the record with key equal to 5 into table
+.BR tmp ,
+which appears as follows:
+.DM
+Item    Amount  Cost    Value   Description   
+----    ------  ----    -----   --------------
+   5        99    24     2376   cleaning cloth
+.DE
+.PP
+The next command blanks the contents of
+.BR tmp ,
+then writes the blanked row back into
+.B inventory
+at the location stored earlier at
+.BR LOCATION :
+.DM
+	blank < tmp | replace inventory $LOCATION
+.DE
+.PP
+.B inventory
+now appears as follows:
+.DM
+Item    Amount  Cost    Value   Description   
+----    ------  ----    -----   --------------
+   1         3    50      150   rubber gloves
+   2       100     5      500   test tubes
+   3         5    80      400   clamps
+   4        23    19      437   plates
+.sp \n(pDu
+   6        89   147    13083   bunsen burners
+   7         5   175      875   scales
+.DE
+.SH "See Also"
+.B
+index,
+lock,
+replace,
+search,
+unlock
+.R
+.SO seek