Shell脚本对行进行切片，并获得第一部分

Question

这里我有一项任务，从有大约1000行的日志文件中提取文件名，日志中的每一行都以文件名开始，后面跟着其他细节，现在我想从每一行中提取每个文件名(绝对路径，从‘./’开始)，并将其放入文件中。示例日志文件具有以下数据。

./plugins-src/rabbitmq-management/src/rabbit_mgmt_wm_overview.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_old_db.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_wm_exchange.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_wm_channel.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_wm_vhosts.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_wm_permission.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_util.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_wm_queue_purge.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_format.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_wm_exchanges.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_wm_bindings.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_wm_definitions.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-management/src/rabbit_mgmt_wm_queue_get.erl:1:%%   The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-federation-management/src/rabbit_federation_mgmt.erl:1:%%  The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-mqtt/src/rabbit_mqtt_processor.erl:1:%% The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-mqtt/src/rabbit_mqtt_util.erl:1:%% The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-mqtt/src/rabbit_mqtt_collector.erl:1:%% The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-mqtt/src/rabbit_mqtt_frame.erl:1:%% The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-mqtt/src/rabbit_mqtt_sup.erl:1:%% The contents of this file are subject to the Mozilla Public License
./plugins-src/rabbitmq-mqtt/src/rabbit_mqtt.erl:1:%% The contents of this file are subject to the Mozilla Public License

有一个冒号(：)可以用作分隔符，它精确地结束每一行中的文件名，但我在shell脚本中没有专门知识来分割它并提取文件名。

Answer 1

 awk -F':' '{print $1}' filename.log

 # OR 

 cut -d':' -f1 filename.log

Answer 2

使用bash的另一个途径是：

while read -r line; do echo "${line%%:*}"; done <filename

它使用参数展开和子字符串删除，这是一组内置字符处理例程。基本上：

var="123:456:789"
echo "${var#*:}"   # 456:789  remove from left to 1st occurrence of ':'
echo "${var%:*}"   # 123:456  remove from right to 1st occurrence of ':'
echo "${var##*:}"  # 789  remove from left to last occurrence of ':'
echo "${var%%:*}"  # 123  remove from right to last occurrence of ':'

(注意：通配符在展开中的位置)

它们甚至可以嵌套。