I have read literally every answer on the net that I could find. Nothing is similar to my problem, so here it is:
I have a bash script with curl and I get a variable back. I want to update my database with this variable, however it doesn't work.
My variable is $stream and no matter what I do, I always get the word "$stream" into the database instead of the result of the curl.
My script is:
#!/bin/bash
stream=$(curl --silent "https://player.mediaklikk.hu/playernew/player.php?video=mtv1live&noflash=yes&output=vast&unviewed_position_start=1&env=vp&impl=s&correlator=&osfamily=Windows&osversion=10&browsername=Chrome&browserversion=97.0.4692.99&title=M1&contentid=mtv1live&embedded=0" | grep -Po 'file": "\K(.*?)(?=")' | sed 's/\\\/\\\//https:\\\/\\\//g')
echo $stream
mysql
use mydatabase;
UPDATE my_table SET my_url = "$stream" WHERE my_name = 'stream_name';
You can use the -e option to execute a query. Put this in double quotes and variables will be expanded.
#!/bin/bash
stream=$(curl --silent "https://player.mediaklikk.hu/playernew/player.php?video=mtv1live&noflash=yes&output=vast&unviewed_position_start=1&env=vp&impl=s&correlator=&osfamily=Windows&osversion=10&browsername=Chrome&browserversion=97.0.4692.99&title=M1&contentid=mtv1live&embedded=0" | grep -Po 'file": "\K(.*?)(?=")' | sed 's/\\\/\\\//https:\\\/\\\//g')
echo $stream
mysql mydatabase -e "UPDATE my_table SET my_url = '$stream' WHERE my_name = 'stream_name';"
I have used the method to assign the SQL output to a variable as below.
dbRole=$(${SQLPLUSPGM} -s / as sysdba <<-EOF
set head off
set verify off
set feedback off
select trim(translate(database_role,' ','_')) from v\$database;
exit;
EOF
)
But the variable o/p appending a "\n" character i.e \nPHYSICAL_STANDBY
However, when I use the below method it is working fine
${SQLPLUSPGM} -s / as sysdba <<-EOF | grep -v '^$' | read dbRole
set head off
set verify off
set feedback off
select trim(translate(database_role,' ','_')) from v\$database;
exit;
EOF
Any suggestion why it is appending `\n' and how we can get rid of it.
Appreciate your suggestions.
Your second method, with the grep -v, removes the additional line.
You can use some filter inside your first method with additional parentheses.
dbRole=$((cat | grep -v "^$") <<-EOF
1
2
3
5
EOF
)
Alternative filters with some differences are grep ., head -1, sed '$d'.
I have a SQL query which contains:
join (&max_dt1) t3
I want to replace &max_dt1 so:
MAX_DT1="'2017-11-03'"
REPLACE="sed -i 's/&max_dt1/select ($MAX_DT1) as dt/g' $FINAL_QUERY"
cat $FINAL_QUERY | eval $REPLACE
Result:
join (select (2017-05-09) as dt) t3
Why is it deleting the quote marks of my variable MAX_DT1?
My real code:
MAX_DT1="'$MAX_DT1'"
echo $MAX_DT1
REPLACE="sed -i 's/&max_dt1/select ($MAX_DT1) as dt/g' $FINAL_QUERY"
echo sed -i "s/&max_dt1/select ($MAX_DT1) as dt/g $FINAL_QUERY
cat $FINAL_QUERY | eval $REPLACE
MAX_DT1 first of all contains just: 2017-11-03
follow this
$ query="join (&max_dt1) t3"
$ MAX_DT1="'2017-11-03'" # <--- you have to quote the single quotes!!
$ sed "s/&max_dt1/select ($MAX_DT1) as dt/g" <<< $query
join (select ('2017-11-03') as dt) t3
Quotes indicates that you affect a string to MAX_DT1 variable. It's not part of your string.
If your variable value has to contains quotes then you have to add them.
For instance:
MAX_DT1="'2017-11-03'"
Unfortunately your Next REPLACE variable won't have what you're expecting and the eval command called later won't work since its sed command would be bad formatted (if you keep your code this way).
Fortunately, your problem is solved if you call directly the sed command this way:
MAX_DT1="'2017-11-03'"
sed -i "s/&max_dt1/select ($MAX_DT1) as dt/g" $FINAL_QUERY
#cat file.txt
12354
13456
13498
#!/bin/bash
for i in `cat file.txt`
do
sqlplus XXXXX/XXXXX#DB_NAME << EOF
select *from TABLE_NAME where id="$i"
EOF
done
This is not working for me. Help me how I can solve this.
The solution given by #codeforester works. However I was unable to use it because it created as many DB connections as the number of lines in your file which is a potential impact.
To overcome this, I chose the below solution which may not be ideal but does the job with just one DB connection.
Considering the same data in file.txt
12354
13456
13498
I used the below sed command to populate the above to a single variable "12354,13456,13498"
myvariable=$(echo "`cat file.txt | sed '$!s/$/,/g' | tr -d '\n' | tr -d ' '`")
Now below script will pass this variable to the SQL query and spool the data into a text file:
#!/bin/bash
myvariable=$(echo "`cat file.txt | sed '$!s/$/,/g' | tr -d '\n' | tr -d ' '`")
echo #myvariable
sqlplus /nolog << EOF
CONNECT user#dbname/dbpassword
SPOOL dboutput.txt
select column1 from table_name where id in ($myvariable);
SPOOL OFF
EOF
The output is stored in dboutput.txt (along with the SQL query)
cat dboutput.txt
SQL> select column1 from table_name where id in (12354,13456,13498);
NAME
---------------------------------------------------------------------------- ----
data1
data2
data3
SQL> spool off
Here is the right way to use the heredoc <<, along with the choice of while read instead of for to read the file:
#!/bin/bash
while read -r value; do
sqlplus xxxxx/xxxxx#db_name << EOF
select * from table_name where id='$value';
# make sure heredoc marker "EOF" is not indented
EOF
done < file.txt
See also:
How can I write a here doc to a file in Bash script?
BashFAQ001 to understand why for loop is not the best way to read text lines from a file.
I needed to write a script to enter multi-line input to a program (psql).
After a bit of googling, I found the following syntax works:
cat << EOF | psql ---params
BEGIN;
`pg_dump ----something`
update table .... statement ...;
END;
EOF
This correctly constructs the multi-line string (from BEGIN; to END;, inclusive) and pipes it as an input to psql.
But I have no idea how/why it works, can some one please explain?
I'm referring mainly to cat << EOF, I know > outputs to a file, >> appends to a file, < reads input from file.
What does << exactly do?
And is there a man page for it?
The cat <<EOF syntax is very useful when working with multi-line text in Bash, eg. when assigning multi-line string to a shell variable, file or a pipe.
Examples of cat <<EOF syntax usage in Bash:
1. Assign multi-line string to a shell variable
$ sql=$(cat <<EOF
SELECT foo, bar FROM db
WHERE foo='baz'
EOF
)
The $sql variable now holds the new-line characters too. You can verify with echo -e "$sql".
2. Pass multi-line string to a file in Bash
$ cat <<EOF > print.sh
#!/bin/bash
echo \$PWD
echo $PWD
EOF
The print.sh file now contains:
#!/bin/bash
echo $PWD
echo /home/user
3. Pass multi-line string to a pipe in Bash
$ cat <<EOF | grep 'b' | tee b.txt
foo
bar
baz
EOF
The b.txt file contains bar and baz lines. The same output is printed to stdout.
This is called heredoc format to provide a string into stdin. See https://en.wikipedia.org/wiki/Here_document#Unix_shells for more details.
From man bash:
Here Documents
This type of redirection instructs the shell to read input from
the current source until a line
containing only word (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 `.
If the redirection operator is <<-, then all leading tab characters
are stripped from input lines and the
line containing delimiter. This
allows here-documents within shell scripts to be indented in a natural fashion.
In your case, "EOF" is known as a "Here Tag". Basically <<Here tells the shell that you are going to enter a multiline string until the "tag" Here. You can name this tag as you want, it's often EOF or STOP.
Some rules about the Here tags:
The tag can be any string, uppercase or lowercase, though most people use uppercase by convention.
The tag will not be considered as a Here tag if there are other words in that line. In this case, it will merely be considered part of the string. The tag should be by itself on a separate line, to be considered a tag.
The tag should have no leading or trailing spaces in that line to be considered a tag. Otherwise it will be considered as part of the string.
example:
$ cat >> test <<HERE
> Hello world HERE <-- Not by itself on a separate line -> not considered end of string
> This is a test
> HERE <-- Leading space, so not considered end of string
> and a new line
> HERE <-- Now we have the end of the string
POSIX 7
kennytm quoted man bash, but most of that is also POSIX 7: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_07_04 :
The redirection operators "<<" and "<<-" both allow redirection of lines contained in a shell input file, known as a "here-document", to the input of a command.
The here-document shall be treated as a single word that begins after the next <newline> and continues until there is a line containing only the delimiter and a <newline>, with no <blank> characters in between. Then the next here-document starts, if there is one. The format is as follows:
[n]<<word
here-document
delimiter
where the optional n represents the file descriptor number. If the number is omitted, the here-document refers to standard input (file descriptor 0).
If any character in word is quoted, the delimiter shall be formed by performing quote removal on word, and the here-document lines shall not be expanded. Otherwise, the delimiter shall be the word itself.
If no characters in word are quoted, all lines of the here-document shall be expanded for parameter expansion, command substitution, and arithmetic expansion. In this case, the <backslash> in the input behaves as the <backslash> inside double-quotes (see Double-Quotes). However, the double-quote character ( '"' ) shall not be treated specially within a here-document, except when the double-quote appears within "$()", "``", or "${}".
If the redirection symbol is "<<-", all leading <tab> characters shall be stripped from input lines and the line containing the trailing delimiter. If more than one "<<" or "<<-" operator is specified on a line, the here-document associated with the first operator shall be supplied first by the application and shall be read first by the shell.
When a here-document is read from a terminal device and the shell is interactive, it shall write the contents of the variable PS2, processed as described in Shell Variables, to standard error before reading each line of input until the delimiter has been recognized.
Examples
Some examples not yet given.
Quotes prevent parameter expansion
Without quotes:
a=0
cat <<EOF
$a
EOF
Output:
0
With quotes:
a=0
cat <<'EOF'
$a
EOF
or (ugly but valid):
a=0
cat <<E"O"F
$a
EOF
Outputs:
$a
Hyphen removes leading tabs
Without hyphen:
cat <<EOF
<tab>a
EOF
where <tab> is a literal tab, and can be inserted with Ctrl + V <tab>
Output:
<tab>a
With hyphen:
cat <<-EOF
<tab>a
<tab>EOF
Output:
a
This exists of course so that you can indent your cat like the surrounding code, which is easier to read and maintain. E.g.:
if true; then
cat <<-EOF
a
EOF
fi
Unfortunately, this does not work for space characters: POSIX favored tab indentation here. Yikes.
Using tee instead of cat
Not exactly as an answer to the original question, but I wanted to share this anyway: I had the need to create a config file in a directory that required root rights.
The following does not work for that case:
$ sudo cat <<EOF >/etc/somedir/foo.conf
# my config file
foo=bar
EOF
because the redirection is handled outside of the sudo context.
I ended up using this instead:
$ sudo tee <<EOF /etc/somedir/foo.conf >/dev/null
# my config file
foo=bar
EOF
<< EoF basically means:
<< - "read the multi-line input that begins from the next line onward, and treat it as if it's code in a separate file"
EoF - "stop reading immediately after the word EoF is found in the multi-line input"
As other answers have explained, the multi-line input is called a Here Document
A Here Document is often used to generate output to be passed to a subsequent process. For example cat << EoF can be used to generate a desired output, using a Here Document.
Here's an example of using a Here Document to create a text document on the fly:
cat << EoF > ./my-document.txt
Hello world
Have a nice day
EoF
A little extension to the above answers. The trailing > directs the input into the file, overwriting existing content. However, one particularly convenient use is the double arrow >> that appends, adding your new content to the end of the file, as in:
cat <<EOF >> /etc/fstab
data_server:/var/sharedServer/authority/cert /var/sharedFolder/sometin/authority/cert nfs
data_server:/var/sharedServer/cert /var/sharedFolder/sometin/vsdc/cert nfs
EOF
This extends your fstab without you having to worry about accidentally modifying any of its contents.
note to mention that cat << \EOT (see the backslash) will not expand any variables inside, while cat << EOT will do.
examples:
FOO="bar"
cat << \EOT > foobar.txt
echo "$FOO"
EOT
will output:
echo $FOO
while:
FOO="bar"
cat << EOT > foobar.txt
echo "$FOO"
EOT
will output:
echo "bar"
Example to create a json file:
cat << EoF > ./allaccess.json
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"s3:*"
],
"Resource": [
"arn:aws:s3:::*"
]
}
]
}
EoF
As a result:
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"s3:*"
],
"Resource": [
"arn:aws:s3:::*"
]
}
]
}
Long story short, EOF marker(but a different literal can be used as well) is a heredoc format that allows you to provide your input as multiline.
A lot of confusion comes from how cat actually works it seems.
You can use cat with >> or > as follows:
$ cat >> temp.txt
line 1
line 2
While cat can be used this way when writing manually into console, it's not convenient if I want to provide the input in a more declarative way so that it can be reused by tools and also to keep indentations, whitespaces, etc.
Heredoc allows to define your entire input as if you are not working with stdin but typing in a separate text editor. This is what Wikipedia article means by:
it is a section of a source code file that is treated as if it were a
separate file.
This isn't necessarily an answer to the original question, but a sharing of some results from my own testing. This:
<<test > print.sh
#!/bin/bash
echo \$PWD
echo $PWD
test
will produce the same file as:
cat <<test > print.sh
#!/bin/bash
echo \$PWD
echo $PWD
test
So, I don't see the point of using the cat command.
Worth noting that here docs work in bash loops too.
This example shows how-to get the column list of table:
export postgres_db_name='my_db'
export table_name='my_table_name'
# start copy
while read -r c; do test -z "$c" || echo $table_name.$c , ; done < <(cat << EOF | psql -t -q -d $postgres_db_name -v table_name="${table_name:-}"
SELECT column_name
FROM information_schema.columns
WHERE 1=1
AND table_schema = 'public'
AND table_name =:'table_name' ;
EOF
)
# stop copy , now paste straight into the bash shell ...
output:
my_table_name.guid ,
my_table_name.id ,
my_table_name.level ,
my_table_name.seq ,
or even without the new line
while read -r c; do test -z "$c" || echo $table_name.$c , | perl -ne
's/\n//gm;print' ; done < <(cat << EOF | psql -t -q -d $postgres_db_name -v table_name="${table_name:-}"
SELECT column_name
FROM information_schema.columns
WHERE 1=1
AND table_schema = 'public'
AND table_name =:'table_name' ;
EOF
)
# output: daily_issues.guid ,daily_issues.id ,daily_issues.level ,daily_issues.seq ,daily_issues.prio ,daily_issues.weight ,daily_issues.status ,daily_issues.category ,daily_issues.name ,daily_issues.description ,daily_issues.type ,daily_issues.owner