How to replace or escape <tab> characters with \t in bash script and being able to output single quotes? - bash

Question

In the goal to create a file from a one line (bash) command, the goal is to output the contents of any text file - in this example a bash script - and wrap each line inside a command that is able to output that same line when pasted in a Terminal window.
Example source input file:
Line 1
Line 2
Line 3
Example desired output:
echo 'Line 1';echo 'Line 2';echo 'Line 3';
Note: whether printf, echo or another command is used to create the output, doesn't matter as long as the source is human readable.
One hurdle were the single quotes, that would not be recreated. Therefore use the form $'string', which are treated specially. The word expands to string, with backslash-escaped characters replaced as specified by the ANSI C standard.
Another requirement is to re-create tab characters from the old file in the new file. Therefore the wish is to replace <\tab> characters with \t.
Our tries to do this with sed or tr fail. How to replace tabs with their escape \t counterpart and still being able to output lines with original quotes?
Input file /Library/Scripts/BootRepairMount.sh contains:
$ cat /Library/Scripts/BootRepairMount.sh
#!/bin/bash
sleep 18
for OUTPUT in $(diskutil list | grep ': Apple_HFS' | awk '{ print $NF }')
do
if [[ -z $(df -lnh | grep /dev/$OUTPUT) ]]; then
echo "$OUTPUT is not mounted, repair and mount"
diskutil repairVolume $OUTPUT
diskutil mount $OUTPUT
fi
done
The best shell one line command we could create is:
$ oldifs=$IFS;printf '\n';printf '{';while IFS= read -r p;do [[ "$p" == *"'"* ]] && echo -n "echo $'$p';" || echo -n "echo '$p';"; done < /Library/Scripts/BootRepairMount.sh | tr '\t' '\134\164';printf '}';printf '\n\n';IFS=$oldifs
Which returns this faulty output:
{echo '#!/bin/bash';echo 'sleep 18';echo $'for OUTPUT in $(diskutil list | grep ': Apple_HFS' | awk '{ print $NF }')';echo 'do';echo '\if [[ -z $(df -lnh | grep /dev/$OUTPUT) ]]; then';echo '\\echo "$OUTPUT is not mounted, repair and mount"';echo '\\diskutil repairVolume $OUTPUT';echo '\\diskutil mount $OUTPUT';echo '\fi';echo 'done';}
Desired output is:
{echo '#!/bin/bash';echo 'sleep 18';echo $'for OUTPUT in $(diskutil list | grep ': Apple_HFS' | awk '{ print $NF }')';echo 'do';echo '\tif [[ -z $(df -lnh | grep /dev/$OUTPUT) ]]; then';echo '\t\techo "$OUTPUT is not mounted, repair and mount"';echo '\t\tdiskutil repairVolume $OUTPUT';echo '\t\tdiskutil mount $OUTPUT';echo '\tfi';echo 'done';}
Bash one line command version 2
$ oldifs=$IFS;printf '\n';printf '{';while IFS= read -r p;do [[ "$p" == *"'"* ]] && printf 'printf $'\''%q'\'';' "$p" || printf 'printf '\''%q'\'';' "$p"; done < /Library/Scripts/BootRepairMount.sh;printf '}';printf '\n\n';IFS=$oldifs
returns output that is heavy escaped:
{printf '\#\!/bin/bash';printf 'sleep\ 18';printf $'for\ OUTPUT\ in\ \$\(diskutil\ list\ \|\ grep\ \':\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ Apple_HFS\'\ \|\ awk\ \'\{\ print\ \$NF\ \}\'\)';printf 'do';printf '$'\tif [[ -z $(df -lnh | grep /dev/$OUTPUT) ]]; then'';printf '$'\t\techo "$OUTPUT is not mounted, repair and mount"'';printf '$'\t\tdiskutil repairVolume $OUTPUT'';printf '$'\t\tdiskutil mount $OUTPUT'';printf '$'\tfi'';printf 'done';}
that never gets unescaped back to its original values in Mac OS X 10.7.5.
printf '\#\!/bin/bash';
outputs:
\#\!/bin/bash
As well as:
echo -e '\#\!/bin/bash'
does output the unescaped value
\#\!/bin/bash
-e is not a valid command switch for the Mac OS X 10.7.5 echo command, according to its man page.

Answer 1

bash's builtin command printf has %q format code that handles this:
printf '\n{ '; while IFS= read -r p; do printf "echo %q; " "$p"; done < /Library/Scripts/BootRepairMount.sh; printf '}\n\n'
Unfortunately, it doesn't always choose quoting/escaping modes that're easy to read. Specifically, it tends to prefer escaping individual metacharacters (e.g. spaces) rather than enclosing them in quotes:
{ echo \#\!/bin/bash; echo sleep\ 18; echo for\ OUTPUT\ in\ \$(diskutil\ list\ \|\ grep\ \':\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ Apple_HFS\'\ \|\ awk\ \'{\ print\ \$NF\ }\'); echo do; echo $'\tif [[ -z $(df -lnh | grep /dev/$OUTPUT) ]]; then'; echo $'\t\techo "$OUTPUT is not mounted, repair and mount"'; echo $'\t\tdiskutil repairVolume $OUTPUT'; echo $'\t\tdiskutil mount $OUTPUT'; echo $'\tfi'; echo done; }

Answer 2

If I understand right you want paste one long line to the Terminal.app and want get the "source code" of original script. So, need a script what will generate the one-line script.
Maybe a bit unusual solution, but it is easy and simple.
here is the test script called test.sh (instead of your BootReapirMount.sh)
for i in {1..10}
do
date
done
Here is the generator script mkecho.sh
#!/bin/bash
[[ ! -f "$1" ]] && echo "Need filename" && exit 1
asc=$(gzip < "$1" | base64)
echo "base64 -D <<<'$asc'| gzip -d"
Now, run:
bash mkecho.sh test.sh
you will get the next:
base64 -D <<<'H4sIAASwqFEAA0vLL1LIVMjMU6g21NMzNKjlSsnn4kxJLEkFMvJSuQBZFmY0HwAAAA=='| gzip -d
If you copy and paste the above into the terminal, it will will display the original test.sh
Variant2
If you want directly execute the script, you should modify the mkecho.sh to the next mkeval.sh
#!/bin/bash
[[ ! -f "$1" ]] && echo "Need filename" && exit 1
asc=$(gzip < "$1" | base64)
echo -n 'eval "$(base64 -D <<<"'
echo -n $asc
echo -n '" | gzip -d)"'
echo
When run
bash mkeval.sh test.sh
will get
eval "$(base64 -D <<<"H4sIAASwqFEAA0vLL1LIVMjMU6g21NMzNKjlSsnn4kxJLEkFMvJSuQBZFmY0HwAAAA==" | gzip -d)"
and finally when you copy and paste it into the terminal, you run the test.sh and will get:
Fri May 31 16:25:08 CEST 2013
... 8 lined deleted...
Fri May 31 16:25:08 CEST 2013
Warning: because the script is NOT TESTED for every possible conditions, nor for redirects and so on - I really don't recommending using the eval verision.

Answer 3

sed 's/\\t/\\/g'
$ echo 'ffsd \tif [[ -z $' | sed 's/\\t/\\/g'
ffsd \if [[ -z $