The fold command wraps each line in an input file to fit a specified width and prints it to the standard output.

# To wrap each line to default width (80 characters):
fold file

# To wrap each line to width "30":
fold -w30 file

# To wrap each line to width "5" and break the line at spaces (puts each space separated word in a new line, words with length > 5 are wrapped):
fold -w5 -s file