How can I wrap text at a certain column size?

You are looking for

fold -w 80 -s text.txt

• -w tells the width of the text, where 80 is standard.
• -s tells to break at spaces, and not in words.

This is the standard way, but there are other systems, which need "-c" instead of "-w".

In addition to fold, take a look at fmt. fmt tries to choose line breaks intelligently to make text look good. It doesn't break long words, rather it wraps only by spaces. It will also join adjacent lines, which is good for prose but bad for log files or other formatted text.

$ cat shxp.txt

O, they have lived long on the alms-basket of words, I marvel thy
master hath not eaten thee for a word; for thou art not so long by the
head as honorificabilitudinitatibus: thou art easier swallowed than a
flap-dragon.

1​) Assured fixed line width with word breaking:

fold -w 20 <shxp.txt

O, they have lived l
ong on the alms-bask
et of words, I marve
l thy master hath no
t eaten thee for a w
ord; for thou art no
t so long by the hea
d as honorificabilit
udinitatibus: thou a
rt easier swallowed
than a flap-dragon.

2​) Assured fixed line width with extraordinary word breaking. A word gets broken only if it is too large to fit in a line:

fold -sw 20 <shxp.txt

O, they have lived
long on the
alms-basket of
words, I marvel thy
master hath not
eaten thee for a
word; for thou art
not so long by the
head as
honorificabilitudini
tatibus: thou art
easier swallowed
than a flap-dragon.

3​) Promising fixed line width without any word breaking. If word is too large to fit in a line, it is still left as it is, so finally some lines may be larger in size than you need:

fmt -w 20 <shxp.txt

O, they have
lived long on the
alms-basket of
words, I marvel
thy master hath
not eaten thee
for a word; for
thou art not so
long by the head as
honorificabilitudinitatibus:
thou art easier
swallowed than
a flap-dragon.