You can set the internal field separator (IFS) variable, and then let it parse into an array. When this happens in a command, then the assignment to IFSreadIFS
This example will parse one line of items separated by ;
IFS=';' read -ra ADDR <<< "$IN"
for i in "${ADDR[@]}"; do
# process "$i"
done
This other example is for processing the whole content of $IN;
while IFS=';' read -ra ADDR; do
for i in "${ADDR[@]}"; do
# process "$i"
done
done <<< "$IN"
Use cut:
echo 'someletters_12345_moreleters.ext' | cut -d'_' -f 2
More generic:
INPUT='someletters_12345_moreleters.ext'
SUBSTRING=$(echo $INPUT| cut -d'_' -f 2)
echo $SUBSTRING
$ cat > test.yaml << EOF
Line 1
Line 2
Line 3
EOF
$ cat test.yaml
The >test.yaml
You can leverage cat
~$ cat file.txt
Hello from file.txt
~$ echo "My final line" | cat file.txt -
Hello from file.txt
My final line
You can also prepend a line, as such:
~$ echo "My final line" | cat - file.txt
My final line
Hello from file.txt
Note that you are not limited to a single line. catcurlcat
~$ curl -s http://perdu.com | cat file.txt -
Hello from file.txt
<html><head><title>Vous Etes Perdu ?</title></head><body><h1>Perdu sur l'Internet ?</h1><h2>Pas de panique, on va vous aider</h2><strong><pre> * <----- vous êtes ici</pre></strong></body></html>
Your problem seems not to be how here-documents work, as you have correctly described their use in script files. It seems that you don’t understand their interactive use. The following is a (much simplified) crash course which will hopefully clarify the matter for you.
Shells, like all Unix processes in general, have input and output streams to read and write data, to and fro. They have at least one input stream (called stdinstdoutstderrcatstdinstdout
Where do input data come from? They can come from other processes sending them, they can be read from files, or they can be typed directly by the user, which is the most normal situation for a shell’s stdinttyttytty
Shells know when their stdinttyuser@host:current_path$PS1$#root
When you execute a script, the shell attaches an input stream to the file containing it, and reads commands from it. If one of the commands contains a here-document, that is, something like <<ENDstdincat
When input is attached to a ttystdinPS2>cat file > file << "END"PS1
Compare the two here documents in the following example:
(yeti@darkstar:6)~/wrk/tmp$ cat ./xyzzy
#!/bin/bash
cat << EOF
Version 1 - Today is $(date)
EOF
cat << 'EOF'
Version 2 - Today is $(date)
EOF
(yeti@darkstar:6)~/wrk/tmp$ ./xyzzy
Version 1 - Today is Sa 21. Jun 08:51:38 CEST 2014
Version 2 - Today is $(date)
There is no difference, and no particular meaning to those two strings, or any others. It's just an arbitrary terminator and you can use almost any string you like.
Of course, the data itself can't contain that particular line, so if your data contains e.g. a shell script that has another here-doc, you'll need to use different terminators in both. Using somewhat descriptive strings may be useful for any future readers of the script.
E.g.
cat > test.sh <<END_OF_SCRIPT
cat <<EOF
hello
EOF
END_OF_SCRIPT
produces test.shhello
There is a difference if you quote the terminator in the line that starts the here-doc, though, it'll prevent expansions in the here-doc data. This prints $i
cat << 'EOF'
$i
EOF
See also:
awk '{$1=$1;print}'
or shorter:
awk '{$1=$1};1'
Would trim leading and trailing space or tab characters1 and also squeeze sequences of tabs and spaces into a single space.
That works because when you assign something to one of the fields, awkprint$1$NFOFS
To also remove blank lines, change it to awk '{$1=$1};NF'NFawkNF0awk000-0e+12
1(and possibly other blank characters depending on the locale and the awk