CODEWITHSUNDEEP
c++stringawkpipeline
MSD
MSD

Reputation: 1407

pipe inside (awk) System command in cpp

I have the awk command wch I want to wrap in system(). 

std::string cmd = "awk -F\|  '{ var1=$2; var2=$5; print var1, var2 }' 1.txt";
system(cmd.c_str());

Getting the error as,

error: unknown escape sequence '\|'

I have tried giving the quotes in different way. But, nothing helps.

Upvotes: 0

Views: 1386

Answers (2)

Tom Fenech
Tom Fenech

Reputation: 74635

You just need to escape the \:

std::string cmd = "awk -F\\|  '{ var1=$2; var2=$5; print var1, var2 }' 1.txt";
//-----------------------^

When you create your C++ string, \ is treated as an escape character, unless you escape it.

Alternatively in this case, you could just quote the delimiter, avoiding the need to escape it:

std::string cmd = "awk -F'|'  '{ print $2, $5 }' 1.txt";

I assume that your script may be more complex that this in reality but I simplified it for you anyway, in case that helps.

A final option, using raw string literals (which are supported in C++11):

std::string cmd = R"awk -F\|  '{ print $2, $5 }' 1.txt";

The R prefix means that the \ is no longer interpreted as an escape character.

Upvotes: 2

Alejandro Teixeira Muñoz
Alejandro Teixeira Muñoz

Reputation: 2768

maybe scaping the -F"|" quotes??

std::string cmd = "awk -F\"|\" '{ var1=$2; var2=$5; print var1, var2 }' 1.txt";
system(cmd.c_str());

Upvotes: 0

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