trouble with name increment

The script appears sane, so I do not see exactly what it wrong unless you have messed up something that is case sensitive, such as your use of the FileName variable when assigning to mystring.

I have cleaned up the base script below:

#!/bin/bash                                                                                                                                                                 
                                                                                                                                                                            
filename="~/Bureau/essai"                                                                                                                                                   
index=1 #I will deal with the incrementation of index after this part works                                                                                                 
mystring="${filename}${index}.mkv" #omce I have a proper index I concatenate the name with index and name extension                                                         
echo ${mystring} # gives ~/Bureau/essai1.mkv seems to be what I expect                                                                                                      
echo "ffmpeg -f alsa .....  -y ${mystring}"

use that script to get the expected output, then try to copy and run the last output line to see if that differs from manual input.

Once you get this working I can help you to handle the name increments and testing to see if files exist.

I took the original script and replaces the ~ with the $HOME variable and it was able to output into the correct file with no new errors, it looks like ffmpeg was having problems dealing with the ~ character when navigating the filesystem.

The choice to use a date based assignment is better for organization and it should lead to no duplication, but it would not hurt to build error handling for duplicate names as a cautionary tool. Do you know how to use bash to check for existing files?

Then here is a good example of filename error handling and implementing a formatted sequence number to force creation of a new valid name.

#!/bin/bash
 
filedir="${HOME}/testscripts/emptydir/"
filename="testfile"
fileext=".txt"
 
# format the date as year-month-date so it can be easily sorted
dt=$(date +"%y-%m-%d")
 
# loop through from 1 to 999
#  adding each three digit number to the filename
#  until a number that does not exist if found,
#  then make the file with the available name
 
# use the seq command to increment a number, it is being formatted
#  as a 3 digit number from 1 to 999
for seqnum in $(seq -f "%03g" 1 999)
do
  # set a filename including the directory, base name,
  #  date, sequence number and the extension
  fullfile="${filedir}${filename}-${dt}-${seqnum}${fileext}"
 
  # test the see if the file exist, first test to see
  #  if it does not exist
  #
  # the ! means NOT
  # the -f tests to see if the file exists
  # so "! -f" means check to see if the file does not exist
  #
  if [ ! -f ${fullfile} ]
  then
    # since the file does not exist, make it
    touch ${fullfile}
    echo "  ${fullfile} has been created"
 
    # exit the loop since the file has been created
    break
  fi
done

Honestly it does not match the proper printf floating point syntax, I have been using it for a while after I found it on the net. I am assuming that the synax is stating to have leading zeros while forcing whole numbers to be three characters long.

filename="~/Bureau/essai"

This assings the character "~" which is not replaced by your home directory. Your command failed because you don't have a file called "~/Bureau/essai"

Now:

filename=~/Bureau/video

You don't know what you are doing there, do you? hehehe That's a binary operator like "==" That has nothing to do with "~" being your home directory!!! The command, however, should work although not with the expected file name

About these:

but this doesn't (replacing ~ with /home/user)
 
 
filename=/home/jaaf/Bureau/video #I am jaaf
 
index=1
 
mystring=${filename}${index}.mkv
 
 
 
ffmpeg -f alsa -ac 1 -i hw:1,0 -acodec flac -f x11grab -s $LARGEUR"x"$HAUTEUR -i :0.0+$DECALAGE_FENETRE -r 15 -vcodec libx264 -vpre lossless_ultrafast  -y  ${mystring}

What's the output? Could it be possible that you didnt have the "Bureau" folder?

General suggestions:

1- ALWAYS ALWAYS ALWAYS use quotes
2- use [[ instead of [
3- ALWAYS use quotes
4- don't use "break" it's bad programming style (generally) and you can do the same with a "while" and a variable to exit
5- did I mention to ALWAYS use quotes?

Regards

wow.. I think I slowly started to love scripting..
Waiting for the prblem to be solved in this case.. :-)

And Marc, ofcourse you mentioned, "ALWAYS", always ;-)