我正在创建一个bash脚本来自动执行某些命令,我在将错误检查写入同一文件时遇到了一些麻烦.
#!/bin/bash touch ErrorLog.txt bro-cut service < conn.log | sort | uniq -c > ProtocolHierarchy.txt if [ $? -eq 0 ]; then echo -e "OK Protocol Hierarchy Created\n" > ErrorLog.txt else echo -e "Failed Creating Protocol Hierarchy\n" > ErrorLog.txt fi bro-cut id.orig_h < dns.log | sort | uniq -c > AllIPAddresses.txt if [ $? -eq 0 ]; then echo -e "OK Created all IP Addresses\n" > ErrorLog.txt else echo -e "Failed Creating all IP Addresses\n" > ErrorLog.txt fi
目标是拥有一个我可以打开的文件,看到所有命令都工作或失败,目前文件看起来像这样
-e OK Created all IP Addresses
当我希望它看起来像这样
OK Protocol Hierarchy Created OK Created all IP Addresses
我真的很喜欢bash脚本,所以任何提示都将不胜感激!
解决方法
打开一次,并多次写入该文件描述符.
# Open (creating or truncating) the output file (only once!) exec 3>ErrorLog.txt # Write a line to that already-open file echo "something" >&3 # Write a second line to that already-open file echo "something else" >&3 # Optional: close the output file (can also be implicit when the script exits) exec 3>&-
另一个常见的习惯是使用>>以附加模式打开,但每行执行一次效率要低得多.
# Open ErrorLog.txt,truncating if it exist,write one line,and close it echo "something" >ErrorLog.txt # Reopen ErrorLog.txt,write an additional line to the end,and close it again echo "something else" >>ErrorLog.txt
将此练习用于您的脚本(并进行其他一些最佳实践改进)如下所示:
#!/bin/bash # not related to file output,but to making sure we detect errors # only works correctly if run with bash,not sh! set -o pipefail ## set exit status based on whole pipeline,not just last command # picking 3,since FD numbers 0-2 are reserved for stdin/stdout/stderr exec 3>ErrorLog.txt if bro-cut service <conn.log | sort | uniq -c >ProtocolHierarchy.txt; then echo "OK Protocol Hierarchy Created" >&3 else echo "Failed Creating Protocol Hierarchy" >&3 fi if bro-cut id.orig_h <dns.log | sort | uniq -c >AllIPAddresses.txt; then echo "OK Created all IP Addresses" >&3 else echo "Failed Creating all IP Addresses" >&3 fi