Questions tagged [here-string]
A special, more compact form of the here-document consisting of <<< followed by a single WORD.
28
questions
0
votes
2answers
91 views
Output tee to stdout while writing to a FD using here-strings
I am trying to output tee while writing to a custom file descriptor. Example:
exec 4>"/tmp/testfile.txt"; # open FD 4
tee -a >&4 <<< "Output this to stdout" # ...
3
votes
1answer
451 views
Why does a Bash 'while' read loop with a command substitution herestring not read the entire input?
Look at this very basic Bash script:
#!/bin/bash
while read l
do
echo $l
echo "next one"
done <<< $(ps aux)
I have several processes on my computer, and the ps aux command works fine in ...
0
votes
0answers
36 views
SSH tty session as a Here String
At my job, the only way that I can switch users is by doing the following:
sudo su - *USER*
In order to run multiple commands as the user (in a script or something), I use here strings and here docs:...
5
votes
1answer
212 views
What is really happening in this command?
When I use the command cat <<< Hey > text.txt text.txt I expect it to write "Hey" in the file text.txt and then display the file. But there is no output. How is bash interpreting it ...
0
votes
2answers
42 views
Ubuntu - How do I pass JSON string to herestring?
Update
I noticed that I am able to pass JSON with this command
command -j /dev/stdin <<< '{"key":"value"}'
However, it does not work if I call it through SSH.
ssh {target} 'command -j /...
-1
votes
2answers
158 views
The need for $1 and $2 for comparison with an here-string
This is a follow up to this question;
I don't know why but I keep misunderstanding the following code, although I try very hard to understand it:
function read_and_verify {
read -p "$1:" tmp1
...
0
votes
2answers
330 views
What is the end of here string?
It seemed to me that the end of a here string is newline. I realize I am wrong:
$ cat <<< hello world
cat: world: No such file or directory
What can signify the end of a here string?
7
votes
1answer
756 views
What are the differences between here document and here string in their purposes? [closed]
In bash, it seems to me both here document and here string can be used for providing strings as stdin inputs. here document may provide an extra features to specify delimiter, which I am not sure if ...
6
votes
2answers
771 views
Are Here-Strings available in ksh88?
I wanted to extract 3 words from a variable in 3 different variables in ksh script. I used this line on ksh93 and it worked fine:
read A B C <<< $line
Got this error for the above command ...
11
votes
3answers
11k views
Cannot create temp file for here-document: Permission denied
[Note: This similar Q concerns the same bash error message. It's been marked a duplicate of this other Q. But because I found a very different source for this error, I will answer my own Q below.]
...
3
votes
3answers
3k views
Redirect content under a new line (without further syntax or arguments)
I tried these ways to append content to a file:
printf "\nsource ~/script.sh" >> /etc/bash.bashrc
echo -e "\nsource ~/script.sh" >> /etc/bash.bashrc
cat >> "/etc/bash.bashrc" <&...
11
votes
2answers
3k views
Why does wc <<<“$string” show a one-byte-longer length than printf “$string” | wc?
Accidentially, I found out that wc counts differently depending on how it gets the input from bash:
$ s='hello'
$ wc -m <<<"$s"
6
$ wc -c <<<"$s"
6
$ printf '%s' "$s" | wc -m
5
$ ...
2
votes
2answers
662 views
From multiline heredocument to a uniline herestring, with line breaks
I have this multilinie heredocument which I desire to translate into a uniline herestring:
cat <<-"PHPCONF" > /etc/php/*/zz_overrides.ini
[PHP]
post_max_size = 200M
upload_max_filesize ...
1
vote
2answers
5k views
How to read a mapfile
I have some code similar to this:
while read -r col1 col2 col3 col4 col5 col6 col7 col8 TRASH; do
echo -e "${col1}\n${col2}\n${col3}\n${col4}\n${col5}\n${col6}\n"
done< <(ll | tail -n+...
-2
votes
3answers
629 views
Append herestring data to a file, if it doesn't already exist in that file (all in one line)
What will be an "elegant" one-line way to append a single line of data into the end of a file, with herestring, if this exact data isn't already in that file?
This is my herestring append pattern:
...
3
votes
3answers
3k views
How can pipe producer tell pipe consumer it has reached 'End of File'?" (un-named-pipe, not named-pipe)
I have an application which requires a producer to send filenames to a consumer, and have producer indicate to the consumer when the last filename has been sent and the end of file has been reached.
...
2
votes
2answers
2k views
Variable not interpreted with 'EOF'
This is my script:
var="lalallalal"
tee file.tex <<'EOF'
text \\ text \\
$var
EOF
Need to use 'EOF' (with quotes) because I can not use double slash (//) otherwise.
However, if I use the ...
2
votes
2answers
3k views
Single line heredocument - Possible in Bash?
I desire to run a cat heredocument in a single row instead the natural syntax of 3 rows (opener, content, and delimiter). My need to do so is mostly aesthetic as the redirected content aimed aimed to ...
11
votes
1answer
1k views
What is the advantage of using bash -c over using a here string?
Is there any real benefit to using bash -c 'some command' over using bash <<< 'some command'
They seem to achieve the same effect.
3
votes
1answer
2k views
Diff between a string and a file
Basically I want to check the difference of the same file before and after a sed
Tried to run:
diff /opt/postTrades.sh <<< $(sed 's/1\ MIN/10\ MIN/g' /opt/postTrades.sh)
and
diff <<&...
3
votes
1answer
9k views
Elegant way of diff'ing two variables?
I have $a and $b. I want to run diff on those.
The best I have come up with is:
diff <(cat <<<"$a") <(cat <<<"$b")
But I have the district feeling that I am missing a clever ...
1
vote
1answer
801 views
Assign a value to a variable inside a loop
I have this code :
HOSTS="host1 host2"
For hostname in ${HOSTS} ;
do ssh -tt ${USERNAME}@${hostname} << EOF
HOSTSN="test"
echo ${HOSTSN}
exit
EOF
Done
The variable HOSTSN is empty, can ...
3
votes
2answers
5k views
unexpected EOF while looking for matching `)'
I'm simply trying to get the output from a sql statement and store in bash variable. I am getting " unexpected EOF while looking for matching `)' " error.
I don't see what i'm doing wrong. Why am I ...
1
vote
0answers
228 views
ksh type with herestring
I wanted to use Here String in conjunction with custom type in KSH. Unfortunately I am not able to tell what I am doing wrong.
#!/bin/ksh
typeset -T Type_t=(
typeset string='aaa'
function fc {
...
10
votes
4answers
3k views
Why does cut fail with bash and not zsh?
I create a file with tab-delimited fields.
echo foo$'\t'bar$'\t'baz$'\n'foo$'\t'bar$'\t'baz > input
I have the following script named zsh.sh
#!/usr/bin/env zsh
while read line; do
<<<$...
1
vote
2answers
2k views
Use variables in here-string
To feed input to an interactive script, I've been using a here-string:
script <<< $'1 2\n3 4\n5 6\nq'
This effectively enters
1 2
3 4
5 6
q
into the script. But how can I replace one of ...
2
votes
3answers
672 views
Extract lines from text with string as input
How can extract lines that match the regexp string ^li from the text (not a file) below using sed or something?
linux
loan
litmus
launch
I tried grep but I couldn't find a way to search within ...
1
vote
1answer
151 views
Openssl generate invalid websocket security code
I need to write websocket server on GAWK. And server must handle user's Sec-WebSocket-Key by following algorithm (from RFC):
Concat key with 258EAFA5-E914-47DA-95CA-C5AB0DC85B11
Take sha-1 in binary ...
