重定向EOF的标准输出

Question

我想将错误和输出流重定向到/dev/null，我在脚本文件中使用了2>&1 /dev/null (如下所示)，但我得到的错误是

"UPDATE 1
UPDATE 1
UPDATE 1
UPDATE 1
ERROR:  syntax error at or near "EOF"
LINE 1: EOF 2>&1 /dev/null"        ^

如何重定向标准输出？

文件：

psql -h xx.xx.xx.xx -U postgres -d dbname 

<<

update rhq_alert_condition set threshold = $critical_threshold  where alert_definition_id = $critical_id;
update rhq_alert_condition set threshold = $critical_threshold  where alert_definition_id = $critical_recovery_id;
update rhq_alert_condition set threshold = $warning_threshold  where alert_definition_id = $warning_id;
update rhq_alert_condition set threshold = $warning_threshold  where alert_definition_id = $warning_recovery_id;

EOF

2>&1 /dev/null

Answer 1

获得的错误消息是由于脚本中的语法错误造成的。

您所使用的此处文档需要使用<<EOF，而不仅仅是<<。

psql -h xx.xx.xx.xx -U postgres -d dbname <<EOF
update rhq_alert_condition set threshold = $critical_threshold  where alert_definition_id = $critical_id;
update rhq_alert_condition set threshold = $critical_threshold  where alert_definition_id = $critical_recovery_id;
update rhq_alert_condition set threshold = $warning_threshold  where alert_definition_id = $warning_id;
update rhq_alert_condition set threshold = $warning_threshold  where alert_definition_id = $warning_recovery_id;
EOF

若要将输出从此重定向到文件：

psql -h xx.xx.xx.xx -U postgres -d dbname >outfile <<EOF
update rhq_alert_condition set threshold = $critical_threshold  where alert_definition_id = $critical_id;
update rhq_alert_condition set threshold = $critical_threshold  where alert_definition_id = $critical_recovery_id;
update rhq_alert_condition set threshold = $warning_threshold  where alert_definition_id = $warning_id;
update rhq_alert_condition set threshold = $warning_threshold  where alert_definition_id = $warning_recovery_id;
EOF

也可以将错误流重定向到同一个文件：

psql -h xx.xx.xx.xx -U postgres -d dbname >outfile 2>&1 <<EOF
update rhq_alert_condition set threshold = $critical_threshold  where alert_definition_id = $critical_id;
update rhq_alert_condition set threshold = $critical_threshold  where alert_definition_id = $critical_recovery_id;
update rhq_alert_condition set threshold = $warning_threshold  where alert_definition_id = $warning_id;
update rhq_alert_condition set threshold = $warning_threshold  where alert_definition_id = $warning_recovery_id;
EOF

若要将错误流转到/dev/null，请改用2>/dev/null。

要让这两个流都转到位桶，请使用>/dev/null 2>&1。

Answer 2

你可以这样做：

命令> /dev/null 2>&1

Answer 3

我猜这个bash示例完成了作者询问的内容：

gnuplot -p << EOF > /dev/null 2>/dev/null
plot 'file.dat'
EOF

我调用了gnuplot而不是psql，但是关于EOF和重定向的想法是一样的。