liveBook · Manning

Sprintf

As explained in Modern C, Third Edition

sprintf is a C standard-library function that formats converted values into a character array without imposing a destination-size limit.

sprintf formats converted values into a character array using the same formatting capabilities as printf and fprintf. It appends a terminating null character and returns the number of characters written before it, but accepts no destination-size limit. section 14.1

Formatting successive values

A formatter can advance through a buffer by adding sprintf's return value: p += sprintf(p, form, nums[i]);. Separators can then be copied after each formatted number.

Apply these safety rules:

  • Provide a buffer known to be large enough; an insufficient buffer can overflow. section 14.1
  • Use snprintf when the formatted output length is unknown; it limits writes and reports truncation through its return value. section 14.1

How Modern C, Third Edition covers it

How deep it goes
Explains formatting, termination, return length, and overflow risk, then defers bounded output to snprintf.
Examples
Uses sprintnumbers to format numbers, insert separators, advance a buffer pointer, and append a newline.
What it assumes
Assumes familiarity with C character arrays, pointers, strings, and printf-style conversion formats.
What you can do after
Apply sprintf when the destination capacity is already known, and select snprintf for unknown-length output.
How it connects
Connects formatting semantics with printf, fprintf, snprintf, character arrays, and buffer overflow.
Cover of Modern C, Third Edition
liveBookmanning.com
Read Modern C, Third Edition on liveBook Get the book at manning.com

Also explained in

Compare how 2 books explain sprintf →

Related concepts

This explainer was generated by Manning's knowledge graph from the text of Modern C, Third Edition. The section links point to the parts of the book it draws on.