In a file, replace blank line by the last line not blank above
Dear All,
In a CSV file, say that a given column has been extracted. In that column, information is missing (i.e. blank lines appear). I would like to replace the blank lines by the last valid line (not blank) previously read.
For example, consider the extract below:
Code:
123
234
543
111
234
198
I would like this extract to be replaced by:
Code:
123
234
234
543
543
543
111
234
234
234
198
198
I wrote a simple script to do the job that reads myfile.txt and writes the result in out.txt:
Code:
MEMVAL=""
LINENUM=0
while read LINE
do
LINENUM=$(($LINENUM+1));
# Test if the line is blank
CURLINE=`echo $LINE | grep -E '^[:space]*$'`
TEST="$?"
if [ $TEST == 0 ]; then
if [ $LINENUM == 1 ]; then # The first line cannot be blank!!
exit 1
else
# Replace current blank line by memorised info in the output data file
echo "$MEMVAL" >> out.txt
fi
else
MEMVAL="$LINE"
# At first init output data file
if [ $LINENUM == 1 ]; then
echo "$LINE" > out.txt
fi
fi
done < myfile.txt
This script does the job, but it takes ages.
Also I guess there are far more efficient ways to do this by using either sed of awk (maybe csvfix in my case).
Would anybody have a suggestion?
Cheers, Bagvian
Moderator's Comments:
Please use CODE tags as required by forum rules!
Last edited by RudiC; 02-24-2017 at 03:56 PM..
Reason: Added CODE tags.
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Hi
I nned cmd to which will help me to replace a line in file with blank line
e.g.
file1
a
b
c
d
e
after running cmd I shud get
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b
c
d
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tabs(1) General Commands Manual tabs(1)NAME
tabs - set tabs on a terminal
SYNOPSIS
tabs [-v[n]] [-ahuUV] file...
DESCRIPTION
The tabs program clears and sets tab-stops on the terminal. This uses the terminfo clear_all_tabs and set_tab capabilities. If either is
absent, tabs is unable to clear/set tab-stops. The terminal should be configured to use hard tabs, e.g.,
stty tab0
OPTIONS
General Options
-Tname
Tell tabs which terminal type to use. If this option is not given, tabs will use the $TERM environment variable. If that is not set,
it will use the ansi+tabs entry.
-d The debugging option shows a ruler line, followed by two data lines. The first data line shows the expected tab-stops marked with
asterisks. The second data line shows the actual tab-stops, marked with asterisks.
-n This option tells tabs to check the options and run any debugging option, but not to modify the terminal settings.
The tabs program processes a single list of tab stops. The last option to be processed which defines a list is the one that determines the
list to be processed.
Implicit Lists
Use a single number as an option, e.g., "-5" to set tabs at the given interval (in this case 1, 6, 11, 16, 21, etc.). Tabs are repeated up
to the right margin of the screen.
Explicit Lists
An explicit list can be defined after the options (this does not use a "-"). The values in the list must be in increasing numeric order,
and greater than zero. They are separated by a comma or a blank, for example,
tabs 1,6,11,16,21
tabs 1 6 11 16 21
Use a '+' to treat a number as an increment relative to the previous value, e.g.,
tabs 1,+5,+5,+5,+5
which is equivalent to the 1,6,11,16,21 example.
Predefined Tab-Stops
X/Open defines several predefined lists of tab stops.
-a Assembler, IBM S/370, first format
-a2 Assembler, IBM S/370, second format
-c COBOL, normal format
-c2 COBOL compact format
-c3 COBOL compact format extended
-f FORTRAN
-p PL/I
-s SNOBOL
-u UNIVAC 1100 Assembler
PORTABILITY
X/Open describes a +m option, to set a terminal's left-margin. None of the entries in the terminal database provide this capability.
The -d (debug) and -n (no-op) options are extensions not provided by other implementations.
Documentation for other implementations states that there is a limit on the number of tab stops. While some terminals may not accept an
arbitrary number of tab stops, this implementation will attempt to set tab stops up to the right margin of the screen, if the given list
happens to be that long.
SEE ALSO tset(1), infocmp(1), ncurses(3NCURSES), terminfo(5).
This describes ncurses version 5.7 (patch 20100109).
tabs(1)
02-24-2017
