Table of Contents
Chapter 2 介绍关于文件的命令，包括文件命名、文件分割、文件查找、文件条件判断、文件输入、文件内容排序除重、文件内容对比、文件首尾
1 file name
重命名文件
rename *.jpg *.png |
临时文件命名，分割文件，提取文件名
1.1 temp file
$(tempfile) $RANDOM $$ is PID of current script
1.2 splitting file
# generate one test file of 100Kb |
1.3 slicing filename
提取文件名 ${VAR%.*} 或者文件后缀名 ${VAR#.*} 。 % 为非贪婪模式，从右至左匹配一个 .* ， # 从左至右匹配一个 .* 。提取方式是贪婪模式是使用两个 %% 或 ## 即可。
name=${file%.*} |
2 find
find your files with find.
2.1 list all files with path
# '\n' as the delimitor |
If there are blanks, use print0.
2.2 search by name
find / -name "*.txt" –print |
name to match files, iname to ignore case. path to match whole file paths.
regex iregex to match file paths based on regular expression, which specify a pattern.
find . ! -name "*.dll" -print |
! is nagating argument. It matches file names that not end with .txt.
prune exclude portion
maxdepth or mindepth specify directory depths.
2.3 search by attributes
atime to last access time
mtime to last modify time
ctime to last metadata modify time
amin, mmin, cmin are minutes, instead of days in atime.
newer specify a reference file to compare timestamp.
find . -type f -atime +7 -size +2k -user allen -perm 644 -delete |
+, -, / are older, last, exact days or minutes.
size to file size, /b, c, w, k, M, G.
user to file owner
perm to file permissions
2.4 operations
delete to delete, instead of print
exec to execute command on files sorted out.
# find . -type f –user root –exec chown allen {} \; |
{} is a match, \; is the end of find.
3 comparison
程序中的条件判断（比较）形成了 流控制
if condition; then |
if condition; then |
[[ condition ]] && true_cmd || false_cmd |
3.1 math comparison
[ $var -eq 0 ] |
- -eq
- equal
- -ne
- not equal
- -gt
- greater than
- -lt
- less than
- -ge
- greater or equal
- -le
- less or equal
3.2 logical comparison
[ $var1 -ne 0 -a $var2 -gt 2 ] |
- -a
- AND
- -o
- OR
3.3 filesystem conditions
[[ -e ~/.bash_aliases ]] && . ~/.bash_aliases |
- -f $var
- true if $file holds a regular file path
- -x $var
- true if $var bolds a executable file path
- -e $var
- true if $var holds an existing file
- -d $var
- true if $var holds a directory path
- -c $var
- true if $var holds a char dev file
- -b $var
- true if $var holds a block dev file
- -w $var
- true if $var holds a writable file
- -r $var
- true if $var holds a readable file
- -L $var
- true if $var holds a symlink
3.4 string conditions / comparisons
[[ $str1 = $str2 ]] # true if $str1 equals $str2 |
4 input
标准输入，或是读取文件，作为脚本输入。输入的其他重要细节之一，是设定分隔符。
4.1 read
- 读取 n 个字符到 to_var 中
- read -n num_chars to_var
- 输出消息的读取
- read -p "message" to_var
- 屏幕不显示输入内容地读取到 to_var
- read -s to_var
- 设定读取字符的超时
- read -t timeout to_var
- 设定读取字符的分隔符
- read -d delim_char to_var
read -n 3 var && echo $var |
4.2 IFS
另一个分隔符工具 : internal field separator. $IFS
4.3 xarg
cat file.txt | xargs |
5 translate
5.1 将输入中的一组字符串转换成另一组字符串。
tr [option] set1 set2 |
5.2 删除特定字符串
cat file.txt | tr -d '0-9' |
5.3 补充特定字符串
cat file.txt | tr -c set1 |
5.4 集合分类
- alnum
- alphanumeric characters
- alpha
- alphabetic characters
- cntrl
- control characters
- digit
- numeric characters
- xdigit
- hexadecimal characters
- graph
- graphic characters
- printable characters
- punct
- punctuation characters
- space
- whitespace characters
- lower
- lower-case alpha
- upper
- upper-case alpha
tr '[:lower:]' '[:upper:]' |
6 sort
排序文件内容，并剔除重复
sort file1.txt file2.txt > sorted.txt sort file1.txt file2.txt -o sorted.txt # numeric sort && reverse order sort -n file.txt sort -r file.txt # specify key of column 2 sort -k 2 file.txt # ignore leading blanks && directory order sort -bd unsorted.txt # sort by months sort -M file.txt # merge sorted files without sorting again sort -m sorted1 sorted2
sort unsorted.txt | uniq |
comm sorted1.txt sorted2.txt |
7 diff
diff file1.txt file2.txt |
8 head & tail
# Print first 10 lines |
# Reading a growing file, using pid |
# Count number of lines |