How to use commands that only work with one file at a time with all the files you select

Many times we need to run a script to convert a pdf into text, convert .doc files into html, etc; The point is that these commands only accept one file at a time and that is very tedious if we need to perform the same task on several files, especially when we do a script.

I propose a solution for this problem using ls, thirst, grep, awk y sh. What we will do is create the correct command line in each row and execute them with sh, and since sh will execute one line at a time, the consumption of ram memory will not increase, which with other methods can even freeze underpowered machines.

Let's see how to carry out this command sequence.

1- The first thing we have to do is introduce the files that will be used through ls:

ls --directory /camino/a/carpeta/*.ext

2- Then we will need these files to pass quotes «/ path / to group of
files«

ls --directory /camino/a/carpeta/*.ext | sed 's/^/"/' | sed 's/$/"/'

3- Now awk it will be ready to receive the data.

ls --directory /camino/a/carpeta/*.ext | sed 's/^/"/' | sed 's/$/"/' | awk '{print $0}'

Because awk has its own language we will need to separate the quotes that we want to appear to quote a text among other functions we will need to use the backslash \ Let's see how to separate some.
Separate a quote

\”

Show a backslash in the output (we will need to type three bars)

\\\

Sometimes we will need an isolating separator, only the text or the quotes that appear within the two backslashes will be output in the output:

'""'\"\'""'

4- Let's see how to rename all the files that are listed using the command mv just to enter a suffix. (Now to list the file we will need to use the combination "$ 0" whenever we need to use it)

ls --directory /camino/a/carpeta/*.ext | sed 's/^/"/' | sed 's/$/"/' | awk '{print "mv "$0" \"`dirname

"$ 0 ″" / Text-any-`basename "$ 0 ″" \ ""} '| sh

Note is added at the end as shown in the previous sequence the combination « | sh »Which redirects the pipeline to this command interpreter

Let's see some examples prepared to create a script.

Examples:

1- Convert all the pdfs that are listed into text files.

ls --directory “$@” | sed 's/^/"/' | sed 's/$/"/' | awk '{print "pdftotext",$0}' | sh

2- Let's say that we want to apply an effect to an image but without modifying the original, let's see an example with the wave effect well known for the Windows XP logo, since it is a flag with wavy effects (to better appreciate this effect it is recommended to use as resulting image with the extension .png).

ls --directory “$@” | sed 's/^/"/' | sed 's/$/"/' | awk '{print FS="convert -wave 25x150

"$0"","\"\`dirname "$0"`/`basename "$0" | sed '"'"s/\\\\.[[:alnum:]]*$//"'"'`-wave.`basename "$0" |
rev | awk -F . \'"'"'\{print $1}\'"'"'\ | rev`'""'\"\'""' "}' | sh

Note: several passes are made in this sequence:

• One to get the folder where the file is located with dirname
• Another to obtain the base name, but removing the extension of said file
• Another to obtain the exemption of said file.

3- Let's now see how to rename a group of files by putting the corresponding number in front of the name (numeric suffix).

ls --directory “$@” | sed 's/^/"/' | sed 's/$/"/' | awk '{print FS="mv "$0" '""'\"\'""'`dirname
"$0"`/"FNR"-`basename "$0"`'""'\"\'""' "}' | sh

Let's see how to put a numeric prefix (put a number at the end, but before the exemption) this option is only valid if the file has a.

ls --directory “$@” | sed 's/^/"/' | sed 's/$/"/' | awk '{print FS="mv "$0" \"`dirname
"$0"`/`basename "$0" | sed '\'s/\\\\.[[:alnum:]]*$//\''`-"FNR".`echo "$0" | rev | awk -F .
'""'\'\'""'{print $1}'""'\'\'""' | rev `\" " }' | sh

4- Let's see an example where we will have to enter data or select a group of functions, taking as an example the case where we remove password protection from several pdf files that have the same password. (In this case we will use zenity as a dialog box)

zenity --entry --hide-text --text "introduzca la clave de desbloqueo" > $HOME/.cat && ls
--directory “$@” | sed 's/^/"/' | sed 's/$/"/' | awk '{print FS="pdftk "$0" input_pw `cat
$HOME/.cat` output \"`dirname "$0"`/`basename "$0" .pdf`-unlock.pdf\" "}' | sh && rm
$HOME/.cat

As you saw, the objective is to make a cat of a file that will be created at the beginning of the line only once and then it will be eliminated once the conversion is complete.

5- Another utility is, when we need to unzip several files compacted in .zip

ls --directory “$@” | sed 's/^/"/' | sed 's/$/"/' | awk '{print "unzip -x "$0" "}' | sh

6- Let's see an example to protect a pdf with a password allowing reading but protected against printing copy or other options, (the options listed in the dialog box will be those that will be allowed in the pdf, if you do not want to allow any of them, then select none).

zenity --separator " " --multiple --text "Seleccione los Opciones que quiere permitir" --column "Opciones" --list "Printing" "DegradedPrinting" "ModifyContents" "CopyContents" "ScreenReaders" "ModifyAnnotations" "AllFeatures" > $HOME/.cat && zenity --entry --hidetext --text "Teclee la contraseña de protección" > $HOME/.cat2 && ls --directory "$@" | sed 's/^/"/' | sed 's/$/"/' | awk '{print FS="echo \"pdftk \\\"`echo "$0"`\\\" output \\\"`dirname "$0"`/`basename "$0" .pdf`-locked.pdf\\\" allow `cat $HOME/.cat` owner_pw \"`cat $HOME/.cat2`\"\" | sh "}' | sh && rm $HOME/.cat $HOME/.cat2

With these examples it is quite exemplified how to use this option to convert, modify or rename several files with a single script and not converting them by hand one by one. The memory consumption with this option is minimal, depending on the command that is being used, since it does not convert them at the same time but one after the other.

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