fold - wrap each input line to fit in specified width.
Display contents of a file with 80 columns width limit:
fold file.txt
Display contents of a file with 50 columns width limit:
fold -w 50 file.txt
Display contents of a file with 50 columns width limit and break at spaces:
fold -w 50 -s file.txt
Display contents of a file with 20 bytes width limit:
fold -b 20 file.txt