Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

If I have really long output from a command (single line) but I know I only want the first [x] (let's say 8) characters of the output, what's the easiest way to get that? There aren't any delimiters.

share|improve this question
up vote 34 down vote accepted

One way is to use cut:

 command | cut -c1-8

This will give you the first 8 characters of each line of output. Since cut is part of POSIX, it is likely to be on most Unices.

share|improve this answer
Note that cut -c selects characters; cut -b or head -c selects bytes. This makes a difference in some locales (in practice, when using UTF-8). – Gilles Oct 24 '10 at 22:07
You also don't have to specify the start index in this case. Saying cut -c-8 will select from character 1 to 8. – Sparhawk May 9 '14 at 5:08
@Steven, cut's equivalent on Windows is? – Pacerier Aug 25 '15 at 13:06
Also command | dd bs=8 count=1 2>/dev/null. Not saying it's shorter or superior. Just another alternative. – dubiousjim Sep 24 '15 at 3:50

These are some other ways to get only first 8 characters.

command | head -c8

command | awk '{print substr($0,1,8);exit}' 

command | sed 's/^\(........\).*/\1/;q'

And if you have bash

echo ${var:0:8}
share|improve this answer
I think the following sed formulation is a bit easier to read: command | sed 's/\(.\{8\}\).*/\1/' or if your sed supports it: command | sed -r 's/(.{8}).*/\1/'; Otherwise, +1 – Steven D Oct 24 '10 at 4:48
Good stuff, but note that head -c counts bytes, not characters. Similarly, among the major Awk implementations, only GNU awk handles multi-byte characters correctly - FreeBSD Awk and Mawk do not. – mklement0 Jul 5 '15 at 17:30

If you have a sufficiently advanced shell (for example, the following will work in Bash, not sure about dash), you can do:

read -n8 -d$'\0' -r <(command)

After executing read ... <(command), your characters will be in the shell variable REPLY. Type help read to learn about other options.

Explanation: the -n8 argument to read says that we want up to 8 characters. The -d$'\0' says read until a null, rather than to a newline. This way the read will continue for 8 characters even if one of the earlier characters is a newline (but not if its a null). An alternative to -n8 -d$'\0' is to use -N8, which reads for exactly 8 characters or until the stdin reaches EOF. No delimiter is honored. That probably fits your needs better, but I don't know offhand how many shells have a read that honors -N as opposed to honoring -n and -d. Continuing with the explanation: -r says ignore \-escapes, so that, for example, we treat \\ as two characters, rather than as a single \.

Finally, we do read ... <(command) rather than command | read ... because in the second form, the read is executed in a subshell which is then immediately exited, losing the information you just read.

Another option is to do all your processing inside the subshell. For example:

$ echo abcdefghijklm | { read -n8 -d$'\0' -r; printf "REPLY=<%s>\n" "$REPLY"; }
share|improve this answer
If you just want to output the 8 chars, and don't need to process them in the shell, then just use cut. – dubiousjim Sep 8 '12 at 14:04
Good to know about read -n <num>; small caveat: Bash 3.x (still current on OS) mistakenly interprets <num> as a byte count and thus fails with multi-byte characters; this has been fixed in Bash 4.x. – mklement0 Jul 6 '15 at 1:41

This is portable:

a="$(command)"             # Get the output of the command.
b="????"                   # as many ? as characters are needed.
echo ${a%"${a#${b}}"}      # select that many chars from $a

To build a string of variable length of characters has its own question here.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.