UNIX Command Line

Input file file.txt has dates in month/day/year format.

$ cat file.txt 
3/4/2013
3/10/2013
10/4/2013
12/10/2012

Required: Add prefix 0 to first and second field if its a single digit.

Awk solution:

$ awk 'BEGIN {FS=OFS="/"} 
    { 
 if (length($1) == 1) $1="0"$1
 if (length($2) == 1) $2="0"$2
        { print }
}' file.txt

Output:

03/04/2013
03/10/2013
10/04/2013
12/10/2012

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- A newbie tutorial on Unix Awk
- Awk if else
- Convert date format in unix using awk and sed

As you know the 'time' command run programs and summarize system resource usage. Here is a way how you can redirect 'time' command output to file. I would recomend you to go through this page to understand more about 'time' command.

e.g. We are executing 'prog.sh' along with 'time' command.

$ time ./prog.sh 
Initiating merge
Merge completed

real	0m8.803s
user	0m0.010s
sys	0m0.000s

#Trying to redirect the output to a file

$ time ./prog.sh > out.txt

real	0m8.804s
user	0m0.020s
sys	0m0.000s

#out.txt content:

$ cat out.txt 
Initiating merge
Merge completed

#So it only redirected the STDOUT of the script executed, but the 'time' command outut is not redirected.
#This is becuase the command time sends it's output to STDERR (instead of STDOUT)
#To capture output of 'time' command:

$ { time ./prog.sh ; } 2> out.txt
Initiating merge
Merge completed

#Now out.txt content:

$ cat out.txt 

real	0m8.303s
user	0m0.010s
sys	0m0.000s

#And to capture output of script as well as time command:

$ { time ./prog.sh ; } &> out.txt

#'out.txt' now has both the outputs.

$ cat out.txt 
Initiating merge
Merge completed

real	0m8.303s
user	0m0.020s
sys	0m0.000s

As I have mentioned in my earlier post on UNIX 'time' command, there's two types of time command available:
1) Shell's in-build time: Gives only scheduler information
2) /usr/bin/time: Gives more information, also allows formatting the output

The second (/usr/bin/time) one accepts output redirection without code block:

$ /usr/bin/time ./prog.sh &> newout.txt

$ cat newout.txt 
Initiating merge
Merge completed
0.00user 0.01system 0:08.30elapsed 0%CPU (0avgtext+0avgdata 5728maxresident)k
0inputs+8outputs (0major+719minor)pagefaults 0swaps

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Here is a simple UNIX bash script that can be used to convert a simple delimited file to a HTML table format. Default delimiter if not mentioned as part of the command line argument to this script will be comma.

#!/bin/sh
#convert_2_html_table.sh 
#Converts a delimited file to a HTML table
#Jadu Saikia http://unstableme.blogspot.in

NOARG=64

#usage function
f_Usage () {
echo "Usage: $(basename $0) -d <delimiter> -f <delimited-file>"
}

#command line args
while getopts d:f: OPTION
do
    case $OPTION in
        d)  DELIMITER=$OPTARG ;;
        f)  INFILE=$OPTARG ;;
    esac
done

#Less than 2 command line argument, throw Usage
[ "$#" -lt 2 ] && f_Usage && exit $NOARG

DEFAULTDELIMITER=","
#If no delimiter is supplied, default delimiter is comma i.e. ,
SEPARATOR=${DELIMITER:-$DEFAULTDELIMITER}

if [ -f "${INFILE}" ]
        then
                printf "<table border=\"1\">"
                sed "s/$SEPARATOR/<\/td><td>/g" $INFILE | while read line
                        do
                                printf "<tr><td>${line}</td></tr>"
                done
                printf "</table>"
                echo
fi

e.g. Input file:

$ cat data.txt 
First Name:Last Name:Points
Alex:Hall:45
Niraj:Kumar:290
Brian:Smith:100

Executing it:

$ ./convert_2_html_table.sh -d ":" -f data.txt  > data.html

 
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