Redirect error out to standard output

io-redirectionMySQL

I can save the error out in the same file as standard out. I have used this method below.
The problem is that the error out is "always" shown at the top. In the example given below the error relates to the second last sql command where value "india" can not be saved. The error message should be shown next to that statement and not at the top of the file.

# cat import.txt
drop table if exists testme;
create table testme (id int , name varchar(255));
insert into testme values (1, 'abc');
insert into testme values (2, 'abc', 'india');
insert into testme values (3, 'xyz');

# mysql test -vvf  < import.txt  >standard.txt 2>&1

# cat standard.txt
ERROR 1136 (21S01) at line 5: Column count doesn't match value count at row 1
--------------
drop table if exists testme
--------------

Query OK, 0 rows affected

--------------
create table testme (id int , name varchar(255))
--------------

Query OK, 0 rows affected

--------------
insert into testme values (1, 'abc')
--------------

Query OK, 1 row affected

--------------
insert into testme values (2, 'abc', 'india')
--------------

--------------
insert into testme values (3, 'xyz')
--------------

Query OK, 1 row affected

The expected output will look something like this…

# mysql test -vvf  < import.txt
--------------
drop table if exists testme
--------------

Query OK, 0 rows affected

--------------
create table testme (id int , name varchar(255))
--------------

Query OK, 0 rows affected

--------------
insert into testme values (1, 'abc')
--------------

Query OK, 1 row affected

--------------
insert into testme values (2, 'abc', 'india')
--------------

ERROR 1136 (21S01) at line 4: Column count doesn't match value count at row 1
--------------
insert into testme values (3, 'xyz')
--------------

Query OK, 1 row affected

The error out should be placed exactly next to the statement that it relates to. Or else the redirected output file is not useful.

Best Answer

This actually has nothing to do with the shell, it's a 'feature' of the mysql command line utility.

Basically when mysql detects that the output isn't going to a terminal, it enables output buffering. This improves performance. However the program apparently sends the success output to STDOUT, and the error output to STDERR (makes sense really), and keeps a separate buffer for each.

The solution is simply to add -n to the mysql command arguments. The -n (or --unbuffered) option disables output buffering.

For example:

mysql test -nvvf  < import.txt  >standard.txt 2>&1

Related Solutions

Bash – Redirect all standard out for rest of script

If you redirect stdout for the rest of the script, then that would include the "cat" command, so you wouldn't see its output, $file could fill up indefinitely with recursive copies of itself (and would if it wouldn't be so small as to let cat see the end of it before starting to write to it).

To redirect stdout from now on, you simply do:

exec > "$file"

But here maybe you want:

#! /bin/bash -
{
  echo spo 
  echo car
} > "$file"

cat < "$file"

You can also do things like:

exec 3>&1 # save stdout as fd 3
exec > "$file"
echo spo
echo car
exec >&3 3>&- # restore stdout and close fd 3
cat < "$file"

(and by the way, the above is what modern shells do internally when you redirect a compound command like { some; code; } > ... (though they use a fd above 10 and set the O_CLOEXEC flag on it so that executed commands don't see it), while the Bourne shell would fork a subshell in that case)

Also note that in the code above, you don't have to restore stdout for the rest of the script, you can do it for the cat command only:

cat < "$file" >&3 3>&-

(the 3>&- (closing fd 3) is not necessary as cat doesn't use its fd 3 anyway but is good practice in the general case, and strictly speaking, we'd have to add it to every command to emulate the O_CLOEXEC behavior of the shell).

bash io-redirection tty – How to Redirect tty to Standard Output

Since you know the contents of prompt_yes_no.sh you can edit them before including them, replacing the /dev/tty by, for example, stdout. Replace your source by

source <(sed 's|/dev/tty|/dev/stdout|g' <$SH_PATH_SRC/prompt_yes_no.sh)

or for older bash, use a temporary file, eg

sed 's|/dev/tty|/dev/stdout|g' <$SH_PATH_SRC/prompt_yes_no.sh >/tmp/file
source /tmp/file

Best Answer

Related Solutions

Bash – Redirect all standard out for rest of script

bash io-redirection tty – How to Redirect tty to Standard Output

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