【面试题】删除/etc/fstab文件中所有以#开头的行的行首的

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1.1.1 删除/etc/fstab文件中所有以#开头的行的行首的# 号及#后面的所有空白字符；

空白字符

• 空格

• 多个空格

• tab键

此题可以分为两个题目:

1. 删除/etc/fstab文件中所有以#开头的行的行首的# 号及#后面的所有空白字符
2. 删除/etc/fstab文件中所有以#开头的行的行首的# 号及#后面的连续的空白字符

1.1.1.1 删除/etc/fstab文件中所有以#开头的行的行首的# 号及#后面的所有空白字符

可以分为两步:哪个是条件，哪个是动作

• 第1步找出以#开头的行
• 第2步在删除这一行中的空白字符和行首的井号
  awk '/^#/{gsub(/^#|[ \t]+/,"")}1' /etc/fstab
sed -r '/^#/s@^#|[ \t]+@@g' /etc/fstab

演示:

原文内容

[root@oldboyedu59 ~]# cat /etc/fstab

#

# /etc/fstab

# Created by anaconda on Tue Mar 26 11:37:39 2019

#

# Accessible filesystems, by reference, are maintained under '/dev/disk'

# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info

#

UUID=1e827748-cc43-4b1d-8bbc-9a85c239782d / xfs defaults 0 0

UUID=29a4ef75-7502-48df-b31c-c7c10264a7c8 /boot xfs defaults 0 0

UUID=60c45f5e-c78d-41fe-aa92-93d10de6def3 swap swap defaults 0 0

awk '/^#/{gsub(/^#|[ \t]+/,"")}1' /etc/fstab

[root@oldboyedu59 ~]# awk '/^#/{gsub(/^#|[ \t]+/,"")}1' /etc/fstab

/etc/fstab

CreatedbyanacondaonTueMar2611:37:392019

Accessiblefilesystems,byreference,aremaintainedunder'/dev/disk'

Seemanpagesfstab(5),findfs(8),mount(8)and/orblkid(8)formoreinfo

UUID=1e827748-cc43-4b1d-8bbc-9a85c239782d / xfs defaults 0 0

UUID=29a4ef75-7502-48df-b31c-c7c10264a7c8 /boot xfs defaults 0 0

UUID=60c45f5e-c78d-41fe-aa92-93d10de6def3 swap swap   defaults 0 0

sed -r '/^#/s@^#|[ \t]+@@g' /etc/fstab

[root@oldboyedu59 ~]# sed -r '/^#/s@^#|[ \t]+@@g' /etc/fstab

/etc/fstab

CreatedbyanacondaonTueMar2611:37:392019

Accessiblefilesystems,byreference,aremaintainedunder'/dev/disk'

Seemanpagesfstab(5),findfs(8),mount(8)and/orblkid(8)formoreinfo

UUID=1e827748-cc43-4b1d-8bbc-9a85c239782d / xfs defaults 0 0

UUID=29a4ef75-7502-48df-b31c-c7c10264a7c8 /boot xfs defaults 0 0

UUID=60c45f5e-c78d-41fe-aa92-93d10de6def3 swap            swap defaults 0 0

1.1.1.2 删除/etc/fstab文件中所有以#开头的行的行首的# 号及#后面的连续的空白字符

• awk '{gsub(/^#[ \t]+/,"")}1' /etc/fstab
• sed -r 's@^#[ \t]+@@g' /etc/fstab

[root@oldboyedu59 ~]# cat /etc/fstab

#

# /etc/fstab

# Created by anaconda on Tue Mar 26 11:37:39 2019

#

# Accessible filesystems, by reference, are maintained under '/dev/disk'

# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info

#

UUID=1e827748-cc43-4b1d-8bbc-9a85c239782d / xfs defaults  0 0

UUID=29a4ef75-7502-48df-b31c-c7c10264a7c8 /boot xfs defaults 0 0

UUID=60c45f5e-c78d-41fe-aa92-93d10de6def3 swap swap defaults 0 0

[root@oldboyedu59 ~]# awk '{gsub(/^#[ \t]+/,"")}1' /etc/fstab

#

/etc/fstab

Created by anaconda on Tue Mar 26 11:37:39 2019

#

Accessible filesystems, by reference, are maintained under '/dev/disk'

See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info

#

UUID=1e827748-cc43-4b1d-8bbc-9a85c239782d /               xfs defaults 0 0

UUID=29a4ef75-7502-48df-b31c-c7c10264a7c8 /boot xfs defaults 0 0

UUID=60c45f5e-c78d-41fe-aa92-93d10de6def3 swap swap defaults 0 0

[root@oldboyedu59 ~]# sed -r 's@^#[ \t]+@@g' /etc/fstab

#

/etc/fstab

Created by anaconda on Tue Mar 26 11:37:39 2019

#

Accessible filesystems, by reference, are maintained under '/dev/disk'

See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info

#

UUID=1e827748-cc43-4b1d-8bbc-9a85c239782d / xfs defaults 0 0

UUID=29a4ef75-7502-48df-b31c-c7c10264a7c8 /boot xfs defaults 0 0

UUID=60c45f5e-c78d-41fe-aa92-93d10de6def3 swap          swap defaults 0 0