read command doesn't wait for input

Question

I have problem executing a simple script in bash. The script is like this:

#! /bin/sh

read -p 'press  [ENTER]  to continue deleting line'
sudo sed -ie '$d' /home/hpccuser/.profile

and when I execute the script with ./script the output is like this:

press  [ENTER]  to continue deleting line./script: 3: read: arg count
[sudo] password for user

I run the read command directly in terminal (copy and paste from script to terminal) and it works fine; it waits for an ENTER to be hit (just like a pause).

Charles Duffy · Accepted Answer · 2014-12-03T17:18:21.500

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Because your script starts with #!/bin/sh rather than #!/bin/bash, you aren't guaranteed to have bash extensions (such as read -p) available, and can rely only on standards-compliant functionality.

See the relevant standards document for a list of functionality guaranteed to be present in read.

In this case, you'd probably want two lines, one doing the print, and the other doing the read:

printf 'press [ENTER] to continue deleting...'
read _

edited Dec 03 '14 at 17:18

answered Apr 01 '13 at 13:34

Charles Duffy

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I checked and my $SHELL was bash. so /bin/sh would launch bash. am I wrong? – mohammadh montazeri Apr 01 '13 at 13:37
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@mohammadhmontazeri `/bin/sh` launches whichever shell is, well, `/bin/sh` -- NOT your `$SHELL`. Moreover, starting bash as `/bin/sh` (in the case where `/bin/sh` is a symlink to `bash`) disables a great deal of functionality. – Charles Duffy Apr 01 '13 at 13:38
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@mohammadhmontazeri See http://mywiki.wooledge.org/BashGuide/Practices#Choose_Your_Shell for more information. – Charles Duffy Apr 01 '13 at 13:39
Thanks for teaching me about `$REPLY` as the default variable used by `read` @CharlesDuffy! – Jess Apr 01 '13 at 13:40
thanks charles, using /bin/bash corrected the script. it was mentioned in last link you sent too. – mohammadh montazeri Apr 01 '13 at 13:53
This doesn't really solve the problem if your shell is `sh` because e.g. Dash does not allow you to call `read` without the name of a variable. – tripleee Dec 03 '14 at 17:09
@tripleee, ooh! Quite right; thank you for the catch. – Charles Duffy Dec 03 '14 at 17:17
God bless you in abundance, Charles! – pnv Mar 07 '16 at 13:06

Pouya · Answer 2 · 2014-12-08T09:13:49.517

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You can do this with echo command too!:

    echo "press  [ENTER]  to continue deleting line"
    read continue

edited Dec 08 '14 at 09:13

answered Oct 10 '14 at 09:36

Pouya

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This doesn't really solve the problem if your shell is `sh` because e.g. Dash does not allow you to call `read` without the name of a variable. – tripleee Dec 03 '14 at 17:10
With `echo` (unless you have one that supports `-n`, which is an optional feature shells aren't required to implement), you get an extra newline this way that isn't present with the original `read -p` code. – Charles Duffy Jul 02 '17 at 19:05

score 1 · Answer 3 · answered May 27 '21 at 06:22

If you use pipe to redirect contents to your function/script it will run your command in a sub-shell and set stdin (0) to a pipe, which can be checked by

$ ls -l /dev/fd/
lr-x------ 1 root root 64 May 27 14:08 0 -> pipe:[2033522138]
lrwx------ 1 root root 64 May 27 14:08 1 -> /dev/pts/11
lrwx------ 1 root root 64 May 27 14:08 2 -> /dev/pts/11
lr-x------ 1 root root 64 May 27 14:08 3 -> /proc/49806/fd

And if you called read/readarray/... command in that function/script, the read command would return immediately whatever read from that pipe as the stdin has been set to that pipe rather than the tty, which explained why read command didn't wait for input. To make read command wait for input in such case you have to restore stdin to tty by exec 0< /dev/tty before the call to read command.

score 0 · Answer 4 · answered Apr 26 '16 at 09:18

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read -p " Ici mon texte " continue

it works on raspbian

answered Apr 26 '16 at 09:18

chr

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Entirely unhelpful. – Dagrooms Aug 23 '17 at 21:55
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The answerer, and those new to this community, may find it helpful to see a more thorough reason behind a downvote. – Todd Oct 19 '18 at 20:45

score 0 · Answer 5 · answered Jun 18 '19 at 10:15

Seems I'm late to the party, but echo -n "Your prompt" && sed 1q does the trick on a POSIX-compliant shell. This prints a prompt, and grabs a line from STDIN.

Alternatively, you could expand that input into a variable:

echo -n "Your prompt"
YOUR_VAR=$(sed 1q)

score 0 · Answer 6 · answered Apr 03 '23 at 04:21

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Try this:

read -p 'press  [ENTER]  to continue deleting line' < /dev/tty

Forces the input to come from the terminal.

Tested/works using bash script on UBUNTU's GNOME terminal.

answered Apr 03 '23 at 04:21

Jay Marm

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read command doesn't wait for input

6 Answers6