Questions tagged [here-string]

A special, more compact form of the here-document consisting of <<< followed by a single WORD.

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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
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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 ...
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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
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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 ...
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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 /...
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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
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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
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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
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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
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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.] ...
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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
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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
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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 ...
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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+...
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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
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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
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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
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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
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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
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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 ...
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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 { ...
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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 ...