Using Sed To Search/Replace Variable In Bash Script

Question

I'm trying to change the date in the first line of a text file by using Sed to replace the previous days date with the current days date.

Below is the code from the bash script that I'm trying to use to accomplish this:

YMD=$(date +%Y%m%d)

ODA=$(date -u +%Y%m%d --date="1 days ago")

mv ${HOMEDIR}/${PATH1}/nws_${VAR}_conus_daily_${ODA}.ctl ${HOMEDIR}/${PATH1}/nws_${VAR}_conus_daily_${YMD}.ctl

sed "s/${ODA}/${YMD}/" ${HOMEDIR}/${PATH1}/nws_${VAR}_conus_daily_${YMD}.ctl

URL1=http://water.weather.gov/${VAR}/p_download_new/${Y}/${M}/${D}/nws_${VAR}_conus_${YMD}.nc

wget -P ${HOMEDIR}/${PATH1}/ -N ${URL1}

The first line in the text file reads as follows:

dset ^grads/data/ahps/nws_precip_conus_20140423.nc

What is problem with your sed?

anubhava
– anubhava

2014-04-23 17:12:21 +00:00
Commented Apr 23, 2014 at 17:12 — anubhava
– anubhava, Commented Apr 23, 2014 at 17:12
Can you show output of cat -vte file.txt?

anubhava
– anubhava

2014-04-23 17:39:53 +00:00
Commented Apr 23, 2014 at 17:39 — anubhava
– anubhava, Commented Apr 23, 2014 at 17:39
paste2.org/ZUAPMYt9

Aaron Perry
– Aaron Perry

2014-04-23 21:28:19 +00:00
Commented Apr 23, 2014 at 21:28 — Aaron Perry
– Aaron Perry, Commented Apr 23, 2014 at 21:28

Sigi · Accepted Answer · 2014-04-24 03:05:06Z

1

If you want sed to change your file, you have to give the -i option, like so:

sed -i "s/${ODA}/${YMD}/" ${HOMEDIR}/${PATH1}/nws_${VAR}_conus_daily_${YMD}.ctl

Otherwise sed will just output the changed file to standard output.

answered Apr 24, 2014 at 3:05

Sigi

1,88414 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Aaron Perry Over a year ago

Hi Sigi! Adding "-i" option after the sed command worked like a charm! Thank you!

hek2mgl · Accepted Answer · 2014-04-23 17:25:03Z

0

Use this:

sed "1s/[0-9]\+\.nc/$(date +%Y%m%d).nc/" file.txt

It replace the numbers before .nc in the first line of file.txt with the output of

date +%Y%m%d

which outputs the current date in the desired format.

Proof of functionality:

Having file.txt as this:

dset ^grads/data/ahps/nws_precip_conus_20140421.nc
bla bla 20140421.nc

Issue the above command:

sed "1s/[0-9]\+\.nc/$(date +%Y%m%d).nc/" file.txt

Output:

dset ^grads/data/ahps/nws_precip_conus_20140423.nc
bla bla 20140421.nc

You see that the date in the first line and only that has been replaced by the current date.

edited Apr 23, 2014 at 17:25

answered Apr 23, 2014 at 17:09

hek2mgl

159k31 gold badges263 silver badges279 bronze badges

3 Comments

Aaron Perry Over a year ago

Hi, I tried using that code but, it still refuses to change the previous days date to the current days date in the first line... Currently, I've got this: sed "1s/[0-9]\+\.nc/$(date +%Y%m%d).nc/" ${HOMEDIR}/${PATH1}/nws_${VAR}_conus_daily_${YMD}.ctl

Aaron Perry Over a year ago

I wonder why this isn't working on my end... Here's the full bash script: paste2.org/1Yh8LcDp Do you spot anything that might be causing this to not work?

Aaron Perry Over a year ago

Thank you. I should also mention that I was just able to get your sample to work in the terminal but, it won't change the line inside the actual file...

Collectives™ on Stack Overflow

Using Sed To Search/Replace Variable In Bash Script

2 Answers 2

1 Comment

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related