Is it possible to pass an argument from a shell script and pass it to a file.
This is what I am essentially trying to achieve:
My script:
#!/bin/bash -
input=$1
DIR=/home/user/
File=$DIR/test.txt
`cat $File` < $input
this is the test.txt:
select * from abc where date=$input;
I am pretty new to this stuff. please help if there's a correct approach to it.
You don't need to use cat but rather echo for this particular scenario.
echo "select * from abc where date='$input'" > test.txt
The double quotes will redirect and WRITE the echo along with the sentence expanded input variable to the text.txt variable.
If you want to append as opposed to write, use:
echo "select * from abc where date='$input'" >> test.txt
So I am creating a variable and I want to echo it with an addition to the end like so:
I have a file: Filename-08-10-2017.txt
I create a variable:
myvariable=Filename*.txt
When I echo that variable:
echo $myvariable
it outputs Filename-08-10-2017.txt
But I want to change the name to .zip
So I am trying to go:
echo $myvariable.zip and have it output Filename-08-10-2017.txt.zip
however it outputs:
Filename*.txt.zip
How do I go about having it output the way I want?
Thanks.
EDIT:
I kind of figured it out.
I saved a new variable as $($myvariable) which saved the output.
The file name comes from glob expansion. If you want to iterate all files by using glob expansion, you can :
myvariable=Filename*.txt
for f in $myvariable; do echo $f; done
If you want to "disable" the glob expansion, e.g. get literial Filename*.txt by echo $myvariable, you can either set -f or just wrap the variable by double quote: echo "$myvariable".
To maniuplate the text you can do something like:
for f in $myvariable; do echo $f"whatever_like_zip"; done
if you want to do some text substitution, you can
for ... echo ${f/%txt/zip} ; done
It will change all txt file name to zip.
Also if you want to rename the file, change the above echo... into
mv "$f" "yourNewNameHere"
Anyway by reading your question I'm not quite clear, what do you really want.
Yuo can use sed
try this
file="test.txt"
newext=$(echo "$file" | sed -e "s|txt|zip|g")
echo $newext
Is there any way we can redirect commented data into txt files using echo command?
For eg:
echo #abcd1
abcd2
abcd3 >> newFile.txt
I need to comment out the entire block that I am redirecting into the text file. Hence, after executing echo, the newFile.txt should look like:
#abcd1
#abcd2
#abcd3
Escape it.
$ echo \#foo > foo
$ cat foo
#foo
I want to print code into a file using cat <<EOF >>:
cat <<EOF >> brightup.sh
!/bin/bash
curr=`cat /sys/class/backlight/intel_backlight/actual_brightness`
if [ $curr -lt 4477 ]; then
curr=$((curr+406));
echo $curr > /sys/class/backlight/intel_backlight/brightness;
fi
EOF
but when I check the file output, I get this:
!/bin/bash
curr=1634
if [ -lt 4477 ]; then
curr=406;
echo > /sys/class/backlight/intel_backlight/brightness;
fi
I tried putting single quotes but the output also carries the single quotes with it. How can I avoid this issue?
You only need a minimal change; single-quote the here-document delimiter after <<.
cat <<'EOF' >> brightup.sh
or equivalently backslash-escape it:
cat <<\EOF >>brightup.sh
Without quoting, the here document will undergo variable substitution, backticks will be evaluated, etc, like you discovered.
If you need to expand some, but not all, values, you need to individually escape the ones you want to prevent.
cat <<EOF >>brightup.sh
#!/bin/sh
# Created on $(date # : <<-- this will be evaluated before cat;)
echo "\$HOME will not be evaluated because it is backslash-escaped"
EOF
will produce
#!/bin/sh
# Created on Fri Feb 16 11:00:18 UTC 2018
echo "$HOME will not be evaluated because it is backslash-escaped"
As suggested by #fedorqui, here is the relevant section from man bash:
Here Documents
This type of redirection instructs the shell to read input from the
current source until a line containing only delimiter (with no
trailing blanks) is seen. All of the lines read up to that point are
then used as the standard input for a command.
The format of here-documents is:
<<[-]word
here-document
delimiter
No parameter expansion, command substitution, arithmetic expansion,
or pathname expansion is performed on word. If any characters in word
are quoted, the delimiter is the result of quote removal on word, and
the lines in the here-document are not expanded. If word is
unquoted, all lines of the here-document are subjected to parameter
expansion, command substitution, and arithmetic expansion. In the
latter case, the character sequence \<newline> is ignored, and \
must be used to quote the characters \, $, and `.
This should work, I just tested it out and it worked as expected: no expansion, substitution, or what-have-you took place.
cat <<< '
#!/bin/bash
curr=`cat /sys/class/backlight/intel_backlight/actual_brightness`
if [ $curr -lt 4477 ]; then
curr=$((curr+406));
echo $curr > /sys/class/backlight/intel_backlight/brightness;
fi' > file # use overwrite mode so that you don't keep on appending the same script to that file over and over again, unless that's what you want.
Using the following also works.
cat <<< ' > file
... code ...'
Also, it's worth noting that when using heredocs, such as << EOF, substitution and variable expansion and the like takes place. So doing something like this:
cat << EOF > file
cd "$HOME"
echo "$PWD" # echo the current path
EOF
will always result in the expansion of the variables $HOME and $PWD. So if your home directory is /home/foobar and the current path is /home/foobar/bin, file will look like this:
cd "/home/foobar"
echo "/home/foobar/bin"
instead of the expected:
cd "$HOME"
echo "$PWD"
Or, using your EOF markers, you need to quote the initial marker so expansion won't be done:
#-----v---v------
cat <<'EOF' >> brightup.sh
#!/bin/bash
curr=`cat /sys/class/backlight/intel_backlight/actual_brightness`
if [ $curr -lt 4477 ]; then
curr=$((curr+406));
echo $curr > /sys/class/backlight/intel_backlight/brightness;
fi
EOF
IHTH
I know this is a two year old question, but this is a quick answer for those searching for a 'how to'.
If you don't want to have to put quotes around anything you can simply write a block of text to a file, and escape variables you want to export as text (for instance for use in a script) and not escape one's you want to export as the value of the variable.
#!/bin/bash
FILE_NAME="test.txt"
VAR_EXAMPLE="\"string\""
cat > ${FILE_NAME} << EOF
\${VAR_EXAMPLE}=${VAR_EXAMPLE} in ${FILE_NAME}
EOF
Will write '"${VAR_EXAMPLE}="string" in test.txt' into test.txt
This can also be used to output blocks of text to the console with the same rules by omitting the file name
#!/bin/bash
VAR_EXAMPLE="\"string\""
cat << EOF
\${VAR_EXAMPLE}=${VAR_EXAMPLE} to console
EOF
Will output '"${VAR_EXAMPLE}="string" to console'
cat with <<EOF>> will create or append the content to the existing file, won't overwrite. whereas cat with <<EOF> will create or overwrite the content.
cat test.txt
hello
cat <<EOF>> test.txt
> hi
> EOF
cat test.txt
hello
hi
cat <<EOF> test.txt
> haiiiii
> EOF
cat test.txt
haiiiii
from the command line to redirect an ouptput to another file I am aware that I can do something like this
$ echo randomText > file.md
I am also aware that, if I want to append the output to the end of the file, I can do something like this
$ echo randomText >> file.md
Now if I cat the content of file.md I will see something like
randomText
randomText
Is there a way to format the output that is being sent to the file. Rather than appending to the end I am hoping to achieve something like this
randomText ----------------------------------- randomText
To do this, I used printf to format the ouput that was being sent to the file.
printf "%10s", "------------------------------------------" > file.md
To append to the same line, yuou could use printf to tab it.
While going through loop you can try this
echo -ne "randomText" >> logfile
# some other actions
echo -ne "--------------------------------------" >> logfile
echo -ne "randomText" >> logfile
In logfile you can now find
randomText--------------------------------------randomText