Adding a line at the beginning of the file with values computed from date

Question

I am using Solaris O/S. Here are the basic stats for UNIX O/S I am using:

$ oslevel
7.1.0.0
$ ps
      PID    TTY  TIME CMD
 10944546  pts/1  0:00 -ksh
 17563840  pts/1  0:00 ps
$

I am need to write a text on the first line of a text file

test.txt

Text I need to add to the first line on test.txt is

MHHHRGFILE (sysdate - First day of 9 months) 99991231

For middle part (sysdate - First day of 9 months), for eg. Today's date is 07/26/2017, I will need to minus 9 months and then first day of that month. Meaning, I will need to print 20161001

Basically I will end up writing:

MHHHRGFILE 20161001 99991231

to the first line of the file test.txt where MHHHRGFILE and 99991231 are staying constant all the time.

Answer 1

Solaris/Aix date

Sadly, there is no solution possible with (only) Solaris/Aix date.

GNU date

If gnu date is available:

Build the date needed in a variable:

$ date +'%Y/%m/01 -9 months'
2017/07/01 -9 months
$ a=$(date +'%Y/%m/01 -9 months')
$ a=$(date -d "$a" +'%Y%m%d')
$ a='MHHHRGFILE ('"$a"') 99991231'
$ echo "$a"
MHHHRGFILE (20161001) 99991231

Or simply:

$ a=$(date -d "$(date +'%Y/%m/01 -9 months')" +'%Y%m%d')
$ a='MHHHRGFILE ('"$a"') 99991231'

Bash

If bash (4.2+) is available: (using 272 days as equivalent to 9 months)

$ TZ=UTC0 printf '%(%Y%m01)T' $(($(date +'%s') - 3600*24*272))
20161001

$ a=$(TZ=UTC0 printf '%(%Y%m01)T' $(($(date +'%s') - 3600*24*272)))

ksh93

If the ksh is available:

$ printf "%(%Y%m%d)T" "9 month ago"

Perl

If perl is available (9 months are aproximated with 3600*24*30*9):

$ perl -e 'use POSIX qw(strftime); print strftime "%Y%m01",localtime(time()- 3600*24*30*9);'
20161001

$ a=$(perl -e 'use POSIX qw(strftime); print strftime "%Y%m01",localtime(time()- 3600*24*30*9);')

Edit the file

Append that variable to the first line of file

$ sed '1s/.*/&'"$a"'/' file >file.new; mv file.new file

That's it.

Answer 2

It's not complicated to do by hand here:

eval "$(date +'y=%Y m=%m')"
m=$((${m#0} - 9)) # need to strip the 0 for shells like bash or some 
                  # ash derivatives (but not ksh) that complain
                  # about an invalid 09 octal number in arithmetic
                  # expressions. Some date implementations support
                  # date +%-m, but that's not standard.
if [ "$m" -le 0 ]; then
  m=$((m + 12)) y=$((y - 1))
fi
if [ "$m" -lt 10 ]; then
  m=0$m # 0-pad single-digit numbers
fi
sed "1s/$/MHHHRGFILE $y${m}01 99991231/" < file > newfile

Answer 3

Here is the final script that works and outputs Text and Date (go back 9 months and picks first day of that month) into a file on "solaris AIX" Kshell.

#!/bin/ksh

eval "$(date +'y=%Y m=%m')"
m=$((${m#0} - 9))

if [ "$m" -le 0 ]; then
  m=$((m + 12)) y=$((y - 1))
fi

echo "$m"
prvdt=$y${m}01
echo $prvdt
a='MHHHRGFILE '"$prvdt"' 99991231'
echo $a


var="$a"
echo $var
destdir=/applic/e396/data/NNA/Dclients_for_FPD.txt
echo 'Destination File is locate at' $destdir

echo $var >> $destdir

The only issue I am having it add's text MHHHRGFILE 20161001 99991231 at the end of file while i need to add it at very top as a first line item.

Please let me know/help my code correctly so It writes output into destination file's first line.