调用cat时悬挂的shell脚本 [英] Shell script hanging when calling cat
问题描述
我有一个Shell脚本，可通过电子邮件将通过crontasks遇到的错误发送给我，如下所示:
I have a shell script which emails me errors encountered via crontasks which looks like the following:
exec >&-;
output="$(cat)";
shopt -s nocasematch
if [[ "$output" == *"error"* || "$output" == *"warning"* ]]; then
echo "$output" | mail -s "Error" my@email.com;
fi
exit 0;
我的crontab如下:
My crontab looks like:
*/1 * * * * /opt/sh/email.sh /usr/bin/php /home/sites/website/app/console my:cli:command >> /var/log/cron.d/ my.cli.command/log 2>&1
该脚本有效，但"cat"似乎挂起:
The script works, but "cat" seem to hang:
root 23083 0.0 0.0 139752 1112 ? S Mar20 0:00 \_ CROND
500 23091 0.0 0.0 106096 1016 ? Ss Mar20 0:00 | \_ /bin/sh -c /usr/bin/php /var/www/website/app/console my:cli:command 2>&1 | /usr/local/bin/email.sh
500 23096 0.0 0.3 463528 27292 ? S Mar20 0:35 | \_ /usr/bin/php /var/www/website/app/console my:cli:command
500 23097 0.0 0.0 106096 1048 ? S Mar20 0:00 | \_ /bin/bash /usr/local/bin/email.sh
500 23101 0.0 0.0 100936 496 ? S Mar20 0:00 | \_ cat
root 12167 0.0 0.0 139752 1276 ? S Mar22 0:00 \_ CROND
500 12183 0.0 0.0 106096 1104 ? Ss Mar22 0:00 | \_ /bin/sh -c /usr/bin/php /var/www/website/app/console my:cli:command 2>&1 | /usr/local/bin/email.sh
500 12185 0.0 0.4 463528 36612 ? S Mar22 0:32 | \_ /usr/bin/php /var/www/website/app/console my:cli:command
500 12186 0.0 0.0 106096 1104 ? S Mar22 0:00 | \_ /bin/bash /usr/local/bin/email.sh
500 12194 0.0 0.0 100936 516 ? S Mar22 0:00 | \_ cat
root 1675 0.0 0.0 139752 1128 ? S Mar25 0:00 \_ CROND
那里有什么主意吗?
推荐答案
它挂起是因为您没有给 cat 进行连接的任何输入，因此它将永远听STDIN.
It is hanging because you're not giving cat any input to concatenate, so it will just listen to STDIN forever.
在手册页中:
cat实用程序按顺序读取文件，并将它们写入标准输出.文件操作数按命令行顺序处理.如果文件是单个破折号(`-')或不存在，则cat从标准输入中读取.如果file是UNIX域套接字，则cat连接到它，然后读取它直到EOF.这补充了inetd(8)中可用的UNIX域绑定功能.
The cat utility reads files sequentially, writing them to the standard output. The file operands are processed in command-line order. If file is a single dash (`-') or absent, cat reads from the standard input. If file is a UNIX domain socket, cat connects to it and then reads it until EOF. This complements the UNIX domain binding capability available in inetd(8).
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