Change file's name using command line arguments Bash [duplicate] - linux

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Change file's numbers Bash
(2 answers)
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I need to implement a script (duplq.sh) that would rename all the text files existing in the current directory using the command line arguments. So if the command duplq.sh pic 0 3 was executed, it would do the following transformation:
pic0.txt will have to be renamed pic3.txt
pic1.txt to pic4.txt
pic2.txt to pic5.txt
pic3.txt to pic6.txt
etc…
So the first argument is always the name of a file the second and the third always a positive digit.
I also need to make sure that when I execute my script, the first renaming (pic0.txt to pic3.txt), does not erase the existing pic3.txt file in the current directory.
Here's what i did so far :
#!/bin/bash
name="$1"
i="$2"
j="$3"
for file in $name*
do
echo $file
find /var/log -name 'name[$i]' | sed -e 's/$i/$j/g'
i=$(($i+1))
j=$(($j+1))
done
But the find command does not seem to work. Do you have other solutions ?

Answer 1

The problem you're trying to solve is actually somewhat tricky, and I don't think you've fully thought it through. For instance, what's the difference between duplq.sh pic 0 3 and duplq.sh pic 2 5 -- it looks like both should just add 3 to the number, or would the second skip "pic0.txt" and "pic1.txt"? What effect would either one have on files named "pic", "pic.txt", "picture.txt", "picture2.txt", "pic2-2.txt", or "pic999.txt".
There are also a bunch of basic mistakes in the script you have so far:
You should (almost) always put variable references in double-qotes, to avoid unexpected word-splitting and wildcard expansion. So, for example, use echo "$file" instead of echo $file. In for file in $name*, you should put double-quotes around the variable but not the *, because you want that to be treated as a wildcard. Hence, the correct version is for file in "$name"*
Don't put variable references in single-quotes, they aren't expanded there. So in the find and sed commands, you aren't passing the variables' values, you're passing literal dollar signs followed by letters. Again, use double-quotes. Also, you don't have a "$" before "name", so it won't be treated as a variable even in double-quotes.
But the find and sed commands don't do what you want anyway. Consider find /var/log -name "name[1]" -- that looks for files named "name1", not "name1" + some extension. And it looks in the current directory and all subdirectories, which I'm pretty sure you don't want. And the "1" ("$i") may not be the number in the current filename. Suppose there are files named "pic0.jpg", "pic0.png", and "pic0.txt" -- on the first iteration, the loop might find all three with a pattern like "pic0*", then on the second and third iterations try to find "pic1*" and "pic2*, which don't exist. On the other hand, suppose there are files named "pic0.txt", "pic5.txt", and "pic8.txt" -- again, it might look for "pic0*" (ok), then "pic1*" (not found), and then "pic2*" (ditto).
Also, if you get to multi-digit numbers, the pattern "name[10]" will match "file0" and "file1", but not "file10". I don't know why you added the brackets there, but they don't do anything you'd want.
You already have the files being listed one at a time in the $file variable, searching again with different criteria just adds confusion.
Also, at no point in the script do you actually rename anything. The find | sed line will (if it works) print the new name for the file, but not actually rename it.
BTW, when you do use the mv command, use either mv -n or mv -i to keep it from silently and irretrievably overwriting files if/when a name conflict occurs.
To prevent overwriting when incrementing file numbers, you need to do the renames in reverse numeric order (i.e. rename "pic3.txt" to "pic6.txt" before renaming "pic0.txt" to "pic3.txt"). This is especially tricky because if you just sort filenames in reverse alphabetic order, you'll get "pic7.txt" before "pic10.txt". But you can't do a numeric sort without removing the "pic" and ".txt" parts first.
IMO this is actually the trickiest problem to be solved in order to get this script to work right. It might be simplest to specify the largest index number as one of the arguments, and have it start there and count down to 0 (looping over numbers rather than files), and then for each number iterate over matching files (e.g. "pic0.jpg", "pic0.png", and "pic0.txt").

Answer 2

So I assume that 0 3 is just a measurement for the difference of old num and new num and equivalent to 1 4 or 100 103.
To avoid overwriting existing files, create a new temp dir, move all affected files there, and move all of them back in the end.
#/bin/bash
#
# duplq.sh pic 0 3
base="$1"
delta=$(( $3 - $2 ))
# echo delta $delta
target=$(mktemp -d)
echo $target
# /tmp/tmp.7uXD2GzqAb
add () {
f="$1"
b="$2"
d=$3
num=${f#./${b}}
# echo -e "file: $f \tnum: $num \tnum + d: $((num + d))" ;
echo -e "$((num + d))" ;
}
for f in $(find -maxdepth 1 -type f -regex ".*/${base}[0-9]+")
do
newnum=$(add "$f" "${base}" $delta)
echo mv "$f" "$target/${base}$newnum"
done
# exit
echo mv $target/${base}* .
First I tried to just use bash syntax, to check, whether removal of the prefix (pic) results in just digits remaining. I also didn't use the extension .txt - this is left as an exercise for the reader. From the question it is unclear - it is never explicitly told, that all files share the same extension, but all files in the example do.
With the -regex ".*/${base}[0-9]+") in find, the values are guaranteed to be just digits.
num=${f#./${b}}
removes from file f the base ("pic"). Delta d is added.
Instead of really moving, I just echoed the mv-command.
#TODO: Implement the file name extension conservation.
And 2 other pitfalls came to my mind: If you have 3 files pic0, pic00 and pic000 they all will be renamed to pic3. And pic08 will be cut into pic and 08, 08 will then be tried to be read as octal number (or 09 or 012129 and so on) and lead to an error.
One way to solve this issue is, that you prepend the extracted number (001 or 018) with a "1", then add 3, and remove the leading 1:
001 1001 1004 004
018 1018 1021 021
but this clever solution leads to new problems:
999 1999 2002 002?
So a leading 1 has to be cut off, a leading 2 has to be reduced by 1. But now, if the delta is bigger, let's say 300:
018 1018 1318 318
918 1918 2218 1218
Well - that seems to be working.