平时查看某些配置文件的时，我们会发现有很多注释（如："#"开头的行），中间还有很多空行，看起来非常费劲，所以在这里总结下如何去除注释和空行的方法。
举例说明
这里选个简单点的文件，来演示下效果，我们可以看到一些空行和注释。
rdb-save-incremental-fsync yes# Redis LFU eviction (see maxmemory setting) can be tuned. However it is a good
# idea to start with the default settings and only change them after investigating
# how to improve the performances and how the keys LFU change over time, which
# is possible to inspect via the OBJECT FREQ command.
#
# There are two tunable parameters in the Redis LFU implementation: the
# counter logarithm factor and the counter decay time. It is important to
# understand what the two parameters mean before changing them.
#
# The LFU counter is just 8 bits per key, it's maximum value is 255, so Redis
# uses a probabilistic increment with logarithmic behavior. Given the value
# of the old counter, when a key is accessed, the counter is incremented in
# this way:
#
# 1. A random number R between 0 and 1 is extracted.
# 2. A probability P is calculated as 1/(old_value*lfu_log_factor+1).
# 3. The counter is incremented only if R < P.
#
# The default lfu-log-factor is 10. This is a table of how the frequency
# counter changes with a different number of accesses with different
# logarithmic factors:
#
# +--------+------------+------------+------------+------------+------------+
# | factor | 100 hits | 1000 hits | 100K hits | 1M hits | 10M hits |
# +--------+------------+------------+------------+------------+------------+
# | 0 | 104 | 255 | 255 | 255 | 255 |
# +--------+------------+------------+------------+------------+------------+
# | 1 | 18 | 49 | 255 | 255 | 255 |
# +--------+------------+------------+------------+------------+------------+
# | 10 | 10 | 18 | 142 | 255 | 255 |
# +--------+------------+------------+------------+------------+------------+
# | 100 | 8 | 11 | 49 | 143 | 255 |
# +--------+------------+------------+------------+------------+------------+
#
# NOTE: The above table was obtained by running the following commands:
#
去除注释和空行的命令
使用 tr命令
grep -v "#" /etc/yum.conf |tr -s '\n'
效果
使用 sed命令
grep -v "#" /etc/yum.conf|sed '/^$/d'
效果和上面一样，这里就不继续贴图了。
使用 awk命令
grep -v "#" /etc/yum.conf |awk '{if($0!="")print}'
使用 grep命令
grep -v "#" /etc/yum.conf |grep -v "^$"
