Want to "slim down" a bash script.

L_Carver · 05-11-2017, 10:46 AM

This is the original script.

Code:

#!/bin/bash
##Exit from the if/then loop with a lower-case X
##Don't mind the insult.
file0=$@
if [ ! -n $file0 ]; then
	echo -en "No file named to get a date from.\nLet's try again.\nEnter a file name."
	read file0
	if [ $file0= "x" ]; then 
		echo "Sod off, rotter!"
		exit 0
	fi
fi
echo "Finds and formats your file date (for file $file0) to use with a 'touch -t' command."
if [ ! -n $file0 ]; then
	echo -en "No file named to get a date from.\nLet's try again.\nEnter a file name."
	read file0
fi
dart=$(/usr/bin/stat -c %y "$file0" | /usr/bin/cut -d. -f1)
dart=${dart//-/}
dart=${dart/ /}
dart2=${dart/:/}
dart=${dart2/:/.}
echo $dart | /usr/bin/xsel -ib
echo -e "Your date (with no delimiters or spaces is:\n\e[7m$dart\e[0m"
echo "It is also on the clipboard -- check Klipper."

I'm sure you can awk or sed lines 19 to 22 to eliminate them, or use something else native to the shell, but I have (first) forgotten how and (second) can't seem to find the procedure on the Web; reading/interpreting the GNU pages on string manipulation got me where I am in the first place.

Carver

BW-userx · 05-11-2017, 10:58 AM

For one in your comments. it is not a loop of any kind because it does not keep repeating itself or runs in a cycle.

sed and awk are not native to the shell. they are called into the shell to be used within it. (someone correct me if I am wrong on that one).

first run

Code:

userx%slackwhere ⚡ scripts ⚡> chmod +x wtf
userx%slackwhere ⚡ scripts ⚡> ./wtf
Finds and formats your file date (for file ) to use with a 'touch -t' command.
/usr/bin/stat: cannot stat '': No such file or directory
./wtf: line 23: /usr/bin/xsel: No such file or directory
Your date (with no delimiters or spaces is:

It is also on the clipboard -- check Klipper.

second run

Code:

userx%slackwhere ⚡ scripts ⚡> ./wtf testfile
Finds and formats your file date (for file testfile) to use with a 'touch -t' command.
./wtf: line 23: /usr/bin/xsel: No such file or directory
Your date (with no delimiters or spaces is:
201705102008.24
It is also on the clipboard -- check Klipper.

the error no file etc.. is account of I don't got xsel

test file

Code:

testfile
id:6
amount:1032
three-there

sed to remove hyphen

Code:

userx%slackwhere ⚡ scripts ⚡> sed 's/-/ /g' testfile
testfile
id:6
amount:1032
three there

sed to replace : colon with . period

Code:

userx%slackwhere ⚡ scripts ⚡> sed 's/:/./g' testfile                                                      
testfile
id.6
amount.1032
three-there

Notice much difference?

ondoho · 05-11-2017, 01:34 PM

i'm intrigued.
what is the script doing? or supposed to?

L_Carver · 05-13-2017, 01:24 AM

Quote:

Originally Posted by ondoho

i'm intrigued.
what is the script doing? or supposed to?

I often download JPEGs I want to keep the server-side modification dates for. This script helps me do so.

Code:

echo "Finds and formats your file date (for file $file0) to use with a 'touch -t' command."

I don't know about your bash, but mine invariably gives me something like

Code:

2017-05-11 23:22:53.553544345 -0400

when I run a stat -c %y" command on a file. My touch with the -t option gives an error on that kind of string, and I'm looking to avoid typing spaces (a string of digits saves time and effort, imo) in the dates I set for changing the dates back after I've run some command-line application such as ImageMagick on them. I used to like touch -d and thought it was OK (i.e., didn't return "Invalid format" errors) with just about every date string I could use, and rather than parse out the date block from an ls command, I figured using stat -c %y gave me the same information. I couldn't find a stat option that gave the date without some kind of delimiter (excepting the one for seconds from the Epoch), so I found string manipulation such as that in the original script a good enough way to go. But as you can see, it costs a lot in lines of code, and I want to "trim" it "down" to something more 'efficient' and (hopefully, too) 'adaptable' in case the maintainers of bash decide to change the rules again (as they obviously did with customizing field separators, and that just since bash 4.0).

I hope this explains what the script is for.

Carver

ondoho · 05-13-2017, 04:36 AM

the script works for me.
i improved it a little (and removed the pointless insult):

Code:

#!/bin/bash

f="$@"

stat_cmd="$(which stat)"
xsel_cmd="$(which xsel)"

[[ "x$stat_cmd" == "x" ]] && exit 1

while [ ! -f "$f" ]; do
	printf "No file named to get a date from.\nLet's try again.\nEnter a file name."
	read f
done

echo "Finds and formats your file date (for file $f) to use with a 'touch -t' command."
if [ ! -n $f ]; then
	echo -en "No file named to get a date from.\nLet's try again.\nEnter a file name."
	read f
fi
dart=$($stat_cmd -c %y "$f")
dart=${dart%%.*}
dart=${dart//-/}
dart=${dart/ /}
dart=${dart/:/}
dart=${dart/:/.}
echo $dart | $xsel_cmd -ib
echo -e "Your date (with no delimiters or spaces is:\n\e[7m$dart\e[0m"
echo "It is also on the clipboard -- check Klipper."
exit 0

i'm sorry i renamed file0 to f - it has no meaning for you, but i'm too lazy to change it back.
you don't need cut; another bash string manip can do that.
instead of using hardcoded paths, i instructed the script to find the actual absolute path to the executable.
i think it's better that way.
the script won't fail if xsel isn't installed.
the output i'm getting is:

Code:

$> testy testfile
Finds and formats your file date (for file testfile) to use with a 'touch -t' command.
Your date (with no delimiters or spaces is:
201705131236.21
It is also on the clipboard -- check Klipper.

isn't that sufficient?

L_Carver · 05-13-2017, 04:06 PM

Quote:

Originally Posted by ondoho

isn't that sufficient?

Indeed. And it may solve the other problem I noticed about this script: when a filename (or variable with a filename as value) is skipped or not entered, the call to "stat" generates a "File not found" error, which I solved another way. The updated part of the script is:

Code:

dart=$(/usr/bin/stat -c %y "$file0" 2>/dev/null | /usr/bin/cut -d. -f1)

Previously, I had the error dump at the end of line 18 (above). I moved it to just after the stat command and now it works.

Quote:

Originally Posted by ondoho

you don't need cut; another bash string manip can do that.

I see that, but just to be sure, is it

Code:

dart=${dart%%.*}

??

Thanks for the help.

Carver

BW-userx · 05-13-2017, 05:36 PM

this is what ya get

Code:

userx%voider ⚡ ~ ⚡> dots=onedot.twodot.threedot.
userx%voider ⚡ ~ ⚡> echo $dots
onedot.twodot.threedot.
userx%voider ⚡ ~ ⚡> cutdot=${dots%%.*}
userx%voider ⚡ ~ ⚡> echo $cutdot
onedot
userx%voider ⚡ ~ ⚡>

cut farthest from the right.

Code:

userx%voider ⚡ ~ ⚡> cutdot=${dots##*.}
userx%voider ⚡ ~ ⚡> echo $cutdot

userx%voider ⚡ ~ ⚡>

cuts farthest from the left

ondoho · 05-14-2017, 01:07 AM

Quote:

Originally Posted by L_Carver

I see that, but just to be sure, is it

Code:

dart=${dart%%.*}

??

yes.
quick version:
http://commandliners.com/2015/04/str...ation-in-bash/
in depth:
http://www.tldp.org/LDP/abs/html/str...ipulation.html

ntubski · 05-28-2017, 12:05 AM

Code:

dart=$(/usr/bin/stat -c %y "$file0" | /usr/bin/cut -d. -f1)
dart=${dart//-/}
dart=${dart/ /}
dart2=${dart/:/}
dart=${dart2/:/.}

Should be the same as

Code:

dart=$(/usr/bin/date --reference="$file0" +%Y%m%d%H%M.%S)