CODEWITHSUNDEEP
bashprintf
bryrup
bryrup

Reputation: 1

printf in bash with double qouted backslashes

I am trying to get bash printf in doubleqoutes to give me the "right" amount of actually printed backslashes... Who is escaping who ? And why does 2 doublequoted backslashes give me 1 printed backslash exactly as 4 doubleqouted backslashes also gives me 1 printed 1 backslash....? Now 6 doubleqouted backslashes gives me 2 printed backslaches and so does 8 doublquoted backslashes ....?? And so on... So what/who is escaping what/who in the amount of bash doubleqouted backslashes...

povje@povje:~$ which bash
/bin/bash
povje@povje:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.5 LTS
Release:        20.04
Codename:       focal

Trying to print doublequoted backslashes with printf in bash:

povje@povje:~$ printf "\\"
\povje@povje:~$ printf "\\\\"
\povje@povje:~$ printf "\\\\\\"
\\povje@povje:~$ printf "\\\\\\\\"
\\povje@povje:~$ printf "\\\\\\\\\\"
\\\povje@povje:~$

so 2doublequoted \ gives me 1 printed
4doubleqouted \ gives me 1 printed
6doubleqouted \ gives me 2 printed
8doubleqouted \ gives me 2 printed
10*doubleqouted \ gives me 3 printed
. .

so why is every second pair of doubleqouted backslahes ignored ?

Upvotes: 0

Views: 78

Answers (1)

choroba
choroba

Reputation: 241848

Backslashes are special in double quotes in bash. You need to escape (i.e. backslash) a backslash in double quotes to get a literal backslash. Use single quotes and you don't need to double backslashes.

Backslashes are also special in printf. You again need to escape (i.e. backslash) a backslash to get it printed.

But if there's a backslash followed by a non-special character in the argument of printf, the backslash gets interpreted as if escaped, i.e.

printf '\'    # prints \
printf '\\'   # prints \ again
printf '\\\'  # prints \\
# ...

Upvotes: 1

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