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string comparison in bash

Hello everyone,
I wrote the following scrip to rename some jpg files to what I hope
is a better organized way to keeping up with them.

Code:

#!/bin/bash 

# Scrip to rename jpg files

num=1

x=$(date +%m%d%y)

skip=${x}

for file in *.jpg; do

    

    if [ "${file%_*.jpg}" = "$skip" ]; then

        echo Skipping file $file

        let num++

        continue 

    fi          



    if [ $num -le 9 ]; then

        mv "$file" "${x}_n00${num}.jpg"

        echo Moving $file

    fi 



    if  [ $num -ge 10 ]; then

        mv "$file" "${x}_n0${num}.jpg" 

        echo Moving $file

    fi 



    let num++



done

The way I have written the scrip is to use the date as the prefix
for the file and later on I plane to use "read" in the scrip so
I can enter other "older dates" for my archive of files.

Now, for my problem as you can see the first "if" statement skips the
files with the prefix of the current date. This is "not" what I want,
but for testing purposes it was what I could understand. I want the
first if statement to skip the files that have the "format" of the
date command. So any file that has "six numbers" before a "_" will be
skipped.

Thanks in advance.

Quote:

Originally Posted by davimint (Post 3033042)

I want the first if statement to skip the files that have the "format" of the date command. So any file that has "six numbers" before a "_" will be skipped.

I would extract the first six characters from the file name and then be sure they are all numbers using grep in this way:

Code:

if echo ${file:0:6} | grep -q ^[0-9]*$

then

    echo first six chars are numbers

else

    echo nope

fi

or something similar.

Just a side note: you can avoid the second and third if statements if you format the number by padding with leading zeros. One method using printf:

Code:

mv "$file" "${x}_n$(printf "%03u" $num).jpg"

Another method using an artifact:

Code:

num=1001

mv "$file" "${x}_n${num:1:3}.jpg"

I'm not too good with bash, but you could try `expr`

Code:

expr "$file" : '[0-9]\{6\}_.*.jpg'

that will evaluate to something other then 0 if true.

If you have bash >=3.0 then you can just do

Code:

[[ "$file" =~ [0-9]{6}_ ]]

Thanks,
Those solutions look great.

David

I just had to post the results of the new scrip.

Thanks angrybanana and colucix.

Code:

#!/bin/bash 

#

# Scrip to change jpg files for my cannon snapshot

#

num=1

echo "Enter you six digit month code"



read x



for file in *.jpg; do



  if echo ${file:0:6} | grep -q ^[0-9]*$; then

        echo skipping file  $file

        let num++

        continue

  else

        mv "$file" "${x}_n$(printf "%03u" $num).jpg"

        echo moving $file to "${x}_n$(printf "%03u" $num).jpg"

    fi

    let num++



done

Everything works great

Need to study up on the read command to make it bullet proof so
I don't enter something stupid.