how to read multiple txt files in c++ in a specified format.?

Question

I have a code in C++ that reads multiple txt files from a directory. But the files are in a specifies format, i.e abc01.txt, abc02.txt, abc03.txt....., abc99.txt.

I can read the file in the format, abc1.txt, abc2.txt, abc3.txt....., abc99.txt. Using my code. Problem is i cant read the integer value 01 to 09.

Please help me how can I edit my code and read all the files.

My code:

 for(files=1;files<=counter;files++) { stringstream out; out<<files; infile="./input/abc"+out.str()+".txt"; input.open(infile.c_str()); }

rpwr021 · Accepted Answer · 2016-12-05 06:02:06Z

This could be a dirty fix but you could add an additional condition to handle text files abc01 to abc09

 for(files=1;files<=counter;files++) { stringstream out; out<<files; if(files<10){ infile="./input/abc0"+out.str()+".txt"; } else infile="./input/abc"+out.str()+".txt"; input.open(infile.c_str()); }

Brutal but simple. Can avoid the stringstream with std::to_string.

Basile Starynkevitch · Accepted Answer · 2016-12-05 05:48:05Z

You could use std::sprintf to format the string, e.g.

for (int filenum=1; filenum<=counter; filenum++) { char nambuf[64]; std::snprintf(nambuf, sizeof(nambuf), "./input/abc%02d.txt", filenum); std::ifstream infile; infile.open(nambuf);

I recommend spending more time reading the documentation of C++ standard library.

Miles Budnek · Accepted Answer · 2016-12-05 05:57:32Z

You can use the std::setw and std::setfill io manipulators to make sure your number is formatted to be at least two digits long:

for(int file = 1; file <= counter; file++) { std::ostringstream filename; filename << "./input/abc" << std::setw(2) << std::setfill('0') << file << ".txt"; std::ifstream input(filename.str()); }

Here inserting std::setw(2) ensures that numbers are formatted to be at least two characters long, and std::setfill('0') fills out any missing characters with '0' when formatting the number.

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