bash <(curl -sSL https://linuxmirrors.cn/main.sh)copy

bash <(curl -sSL https://linuxmirrors.cn/docker.sh)copy

bash <(curl -sSL https://linuxmirrors.cn/docker.sh) --only-registrycopy

type somethingcopy

type cd

cd is a shell builtincopy

  Change attributes of files or directories.
  More information: <https://manned.org/chattr>.

  Make a file or directory [i]mmutable to changes and deletion, even by superuser:

      chattr +i path/to/file_or_directory

  Make a file or directory mutable:

      chattr -i path/to/file_or_directory

  [R]ecursively make an entire directory and contents immutable:

      chattr -R +i path/to/directory

  Mark a directory and its files to be interpreted in a case-insensitive manner (case-[F]olding):

      chattr +F path/to/directory

  Set a file to only allow [a]ppending:

      chattr +a path/to/filecopy

find . -name "*.md" -type f -exec grep -lE "Finished" {} + | while read file; do
  if ! grep -q "2025-05-31" "$file"; then
    number=$(awk '/^pages: [0-9]+/ {print $2}' "$file")
    if [ -n "$number" ]; then
      sed -i "/Finished/i\\- 2025-05-31: $number" "$file"
      echo "已处理: $file - 插入: - 2025-05-31: $number"
    else
      echo "跳过: $file (未找到pages数字或有效日期)"
    fi
  else
    echo "排除: $file (包含 2025-05-31)"
  fi
donecopy

# 创建备份和日志
backup_dir="backup_$(date +%Y%m%d)"
mkdir -p "$backup_dir"
log_file="replace_log.txt"

echo "开始替换操作 $(date)" > "$log_file"

find . -name "*.md" -type f | while read file; do
    # 检查文件是否包含目标字符串
    if grep -q "- 2025-06-01: Finished" "$file"; then
        # 创建备份
        cp "$file" "$backup_dir/$(basename "$file")"
        # 执行替换
        sed -i 's/- 2025-06-01: Finished/- 2025-05-31: Finished/g' "$file"
        # 记录日志
        echo "已修改: $file" >> "$log_file"
        # 显示变更
        echo "=== $file 修改内容 ==="
        diff "$backup_dir/$(basename "$file")" "$file" || true
    else
        echo "无修改: $file" >> "$log_file"
    fi
done

echo "操作完成，备份在 $backup_dir，日志见 $log_file"copy

find . -name "*.md" -type f -exec grep -l "lists: book" {} + | \
while read file; do
    if ! grep -q "Finished" "$file"; then
        # 确保文件末尾有空行（避免追加内容粘连）
        [ -n "$(tail -c 1 "$file")" ] && echo >> "$file"
        # 追加内容
        echo "- 2025-06-01: Finished" >> "$file"
        echo "已处理: $file"
    else
        echo "跳过: $file (已包含 Finished)"
    fi
donecopy

find . -name "*.md" -type f -exec grep -L "Finished" {} + | while read file; do
    awk 'BEGIN {done=0} /^---/ && !done {print; print "- 2025-06-01: Finished"; done=1; next} 1' "$file" > tmp && mv tmp "$file"
donecopy

sudo chattr +i /etc/resolv.conf  # 设置文件不可修改
sudo chattr -i /etc/resolv.conf  # 解除copy

file --mime-type -L filecopy

#!/bin/sh

FILETYPE=$(xdg-mime query filetype $1)
APP=$( find /usr/share -type f -name "*.desktop" -printf "%p\n" | sed 's/\/.*\///g' | rofi -threads 0 -dmenu -i -p "select default app")
echo $APP
xdg-mime default "$APP" "$FILETYPE"
echo "$APP set as default application to open $FILETYPE"copy

stat /

  File: /
  Size: 122       	Blocks: 0          IO Block: 4096   directory
Device: 0,28	Inode: 256         Links: 1
Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2025-05-10 23:46:03.122616066 +0800
Modify: 2025-05-11 21:26:49.474145593 +0800
Change: 2025-05-11 21:26:49.474145593 +0800
 Birth: 2025-01-01 14:58:38.377746860 +0800copy

  Display the type of command the shell will execute.
  Note: All examples are not POSIX compliant.
  More information: <https://www.gnu.org/software/bash/manual/bash.html#index-type>.

  Display the type of a command:

      type command

  Display all locations containing the specified executable (works only in Bash/fish/Zsh shells):

      type -a command

  Display the name of the disk file that would be executed (works only in Bash/fish/Zsh shells):

      type -p command

  Display the type of a specific command, alias/keyword/function/builtin/file (works only in Bash/fish shells):

      type -t commandcopy

Usage: date [OPTION]... [+FORMAT]
  or:  date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]
Display date and time in the given FORMAT.
With -s, or with [MMDDhhmm[[CC]YY][.ss]], set the date and time.

Mandatory arguments to long options are mandatory for short options too.
  -d, --date=STRING          display time described by STRING, not 'now'
      --debug                annotate the parsed date,
                              and warn about questionable usage to stderr
  -f, --file=DATEFILE        like --date; once for each line of DATEFILE
  -I[FMT], --iso-8601[=FMT]  output date/time in ISO 8601 format.
                               FMT='date' for date only (the default),
                               'hours', 'minutes', 'seconds', or 'ns'
                               for date and time to the indicated precision.
                               Example: 2006-08-14T02:34:56-06:00
  --resolution               output the available resolution of timestamps
                               Example: 0.000000001
  -R, --rfc-email            output date and time in RFC 5322 format.
                               Example: Mon, 14 Aug 2006 02:34:56 -0600
      --rfc-3339=FMT         output date/time in RFC 3339 format.
                               FMT='date', 'seconds', or 'ns'
                               for date and time to the indicated precision.
                               Example: 2006-08-14 02:34:56-06:00
  -r, --reference=FILE       display the last modification time of FILE
  -s, --set=STRING           set time described by STRING
  -u, --utc, --universal     print or set Coordinated Universal Time (UTC)
      --help        display this help and exit
      --version     output version information and exit

All options that specify the date to display are mutually exclusive.
I.e.: --date, --file, --reference, --resolution.

FORMAT controls the output.  Interpreted sequences are:

  %%   a literal %
  %a   locale's abbreviated weekday name (e.g., Sun)
  %A   locale's full weekday name (e.g., Sunday)
  %b   locale's abbreviated month name (e.g., Jan)
  %B   locale's full month name (e.g., January)
  %c   locale's date and time (e.g., Thu Mar  3 23:05:25 2005)
  %C   century; like %Y, except omit last two digits (e.g., 20)
  %d   day of month (e.g., 01)
  %D   date (ambiguous); same as %m/%d/%y
  %e   day of month, space padded; same as %_d
  %F   full date; like %+4Y-%m-%d
  %g   last two digits of year of ISO week number (ambiguous; 00-99); see %G
  %G   year of ISO week number; normally useful only with %V
  %h   same as %b
  %H   hour (00..23)
  %I   hour (01..12)
  %j   day of year (001..366)
  %k   hour, space padded ( 0..23); same as %_H
  %l   hour, space padded ( 1..12); same as %_I
  %m   month (01..12)
  %M   minute (00..59)
  %n   a newline
  %N   nanoseconds (000000000..999999999)
  %p   locale's equivalent of either AM or PM; blank if not known
  %P   like %p, but lower case
  %q   quarter of year (1..4)
  %r   locale's 12-hour clock time (e.g., 11:11:04 PM)
  %R   24-hour hour and minute; same as %H:%M
  %s   seconds since the Epoch (1970-01-01 00:00 UTC)
  %S   second (00..60)
  %t   a tab
  %T   time; same as %H:%M:%S
  %u   day of week (1..7); 1 is Monday
  %U   week number of year, with Sunday as first day of week (00..53)
  %V   ISO week number, with Monday as first day of week (01..53)
  %w   day of week (0..6); 0 is Sunday
  %W   week number of year, with Monday as first day of week (00..53)
  %x   locale's date (can be ambiguous; e.g., 12/31/99)
  %X   locale's time representation (e.g., 23:13:48)
  %y   last two digits of year (ambiguous; 00..99)
  %Y   year
  %z   +hhmm numeric time zone (e.g., -0400)
  %:z  +hh:mm numeric time zone (e.g., -04:00)
  %::z  +hh:mm:ss numeric time zone (e.g., -04:00:00)
  %:::z  numeric time zone with : to necessary precision (e.g., -04, +05:30)
  %Z   alphabetic time zone abbreviation (e.g., EDT)

By default, date pads numeric fields with zeroes.
The following optional flags may follow '%':

  -  (hyphen) do not pad the field
  _  (underscore) pad with spaces
  0  (zero) pad with zeros
  +  pad with zeros, and put '+' before future years with >4 digits
  ^  use upper case if possible
  #  use opposite case if possible

After any flags comes an optional field width, as a decimal number;
then an optional modifier, which is either
E to use the locale's alternate representations if available, or
O to use the locale's alternate numeric symbols if available.

Examples:
Convert seconds since the Epoch (1970-01-01 UTC) to a date
  $ date --date='@2147483647'

Show the time on the west coast of the US (use tzselect(1) to find TZ)
  $ TZ='America/Los_Angeles' date

Show the local time for 9AM next Friday on the west coast of the US
  $ date --date='TZ="America/Los_Angeles" 09:00 next Fri'copy

nohup onedrivegui & > /dev/nullcopy

awk '{print $5}' path/to/filecopy

awk '/foo/ {print $2}' path/to/filecopy

awk -F ',' '{print $NF}' path/to/filecopy

awk '{s+=$1} END {print s}' path/to/filecopy

awk 'NR%3==1' path/to/filecopy

awk '{if ($1 == "foo") print "Exact match foo"; else if ($1 ~ "bar") print "Partial match bar"; else print "Baz"}' path/to/filecopy

awk '($10 >= min_value && $10 <= max_value)'copy

awk 'BEGIN {FS=":";printf "%-20s %6s %25s\n", "Name", "UID", "Shell"} $4 >= 1000 {printf "%-20s %6d %25s\n", $1, $4, $7}' /etc/passwdcopy

$ awk -F: '{print $1, $NF}' /etc/passwdcopy

BEGIN          {<initializations>}
   <pattern 1> {<program actions>}
   <pattern 2> {<program actions>}
   ...
END            {< final actions >}copy

awk '
    BEGIN { print "\n>>>Start" }
    !/(login|shutdown)/ { print NR, $0 }
    END { print "<<<END\n" }
' /etc/passwdcopy

          $1      $2/$(NF-1)    $3/$NF
           ▼          ▼           ▼
        ┌──────┬──────────────────┬───────┐
$0/NR ▶ │  ID  │  WEBSITE         │  URI  │
        ├──────┼──────────────────┼───────┤
$0/NR ▶ │  1   │  cheatsheets.zip │  awk  │
        ├──────┼──────────────────┼───────┤
$0/NR ▶ │  2   │  google.com      │  25   │
        └──────┴──────────────────┴───────┘copy

# First and last field
awk -F: '{print $1,$NF}' /etc/passwd

# With line number
awk -F: '{print NR, $0}' /etc/passwd

# Second last field
awk -F: '{print $(NF-1)}' /etc/passwd

# Custom string
awk -F: '{print $1 "=" $6}' /etc/passwdcopy

awk 'BEGIN {print "hello world"}'        # Prints "hello world"
awk -F: '{print $1}' /etc/passwd         # -F: Specify field separator

# /pattern/ Execute actions only for matched pattern
awk -F: '/root/ {print $1}' /etc/passwd

# BEGIN block is executed once at the start
awk -F: 'BEGIN { print "uid"} { print $1 }' /etc/passwd

# END block is executed once at the end
awk -F: '{print $1} END { print "-done-"}' /etc/passwdcopy

awk -F: '$3>30 {print $1}' /etc/passwdcopy

awk 'BEGIN{
    while (a++ < 1000)
        s=s " ";
    print s
}'copy

awk 'BEGIN {
   fruits["mango"] = "yellow";
   fruits["orange"] = "orange"
   for(fruit in fruits) {
     print "The color of " fruit " is " fruits[fruit]
   }
}'copy

# => 5
awk 'BEGIN{print length("hello")}'
# => HELLO
awk 'BEGIN{print toupper("hello")}'
# => hel
awk 'BEGIN{print substr("hello", 1, 3)}'copy

awk -F: '{sum += $3}
     END { print sum, sum/NR }
' /etc/passwdcopy

awk 'BEGIN {
    for (i = 1; i < ARGC; i++)
        print ARGV[i] }' a b ccopy

awk 'BEGIN { FS=":";OFS=","}
    {print $1,$2,$3,$4}' /etc/passwdcopy

awk 'BEGIN {
    if (match("One Two Three", "Tw"))
        print RSTART }'copy

awk 'BEGIN {
    if (match("One Two Three", "re"))
        print RLENGTH }'copy

awk -v var1="Hello" -v var2="Wold" '
    END {print var1, var2}
' </dev/nullcopy

awk -v varName="$PWD" '
    END {print varName}' </dev/nullcopy

awk 'BEGIN {
    if ("foo" ~ "^fo+$")
        print "Fooey!";
}'copy

awk 'BEGIN {
    if ("boo" !~ "^fo+$")
        print "Boo!";
}'copy

awk 'BEGIN {
    assoc["foo"] = "bar";
    assoc["bar"] = "baz";
    if ("foo" in assoc)
        print "Fooey!";
}'copy

awk '
    # Returns minimum number
    function find_min(num1, num2){
       if (num1 < num2)
       return num1
       return num2
    }
    # Returns maximum number
    function find_max(num1, num2){
       if (num1 > num2)
       return num1
       return num2
    }
    # Main function
    function main(num1, num2){
       result = find_min(num1, num2)
       print "Minimum =", result

       result = find_max(num1, num2)
       print "Maximum =", result
    }
    # Script execution starts here
    BEGIN {
       main(10, 60)
    }
'copy

awk 'BEGIN {
    arr[0] = "foo";
    arr[1] = "bar";
    print(arr[0]); # => foo
    delete arr[0];
    print(arr[0]); # => ""
}'copy

awk 'BEGIN {
    assoc["foo"] = "bar";
    assoc["bar"] = "baz";
    print("baz" in assoc); # => 0
    print("foo" in assoc); # => 1
}'copy

awk 'BEGIN {
    split("foo:bar:baz", arr, ":");
    for (key in arr)
        print arr[key];
}'copy

awk 'BEGIN {
    arr[0] = 3
    arr[1] = 2
    arr[2] = 4
    n = asort(arr)
    for (i = 1; i <= n ; i++)
        print(arr[i])
}'copy

awk 'BEGIN {
    multidim[0,0] = "foo";
    multidim[0,1] = "bar";
    multidim[1,0] = "baz";
    multidim[1,1] = "boo";
}'copy

awk 'BEGIN {
    array[1,2]=3;
    array[2,3]=5;
    for (comb in array) {
        split(comb,sep,SUBSEP);
        print sep[1], sep[2],
        array[sep[1],sep[2]]
    }
}'copy

awk -v count=2 'BEGIN {
    if (count == 1)
        print "Yes";
    else
        print "Huh?";
}'copy

awk -v count=2 'BEGIN {
    print (count==1) ? "Yes" : "Huh?";
}'copy

awk 'BEGIN {
    assoc["foo"] = "bar";
    assoc["bar"] = "baz";
    if ("foo" in assoc)
        print "Fooey!";
}'copy

awk 'BEGIN {
    assoc["foo"] = "bar";
    assoc["bar"] = "baz";
    if ("Huh" in assoc == 0 )
        print "Huh!";
}'copy

awk -F: '{
    switch (NR * 2 + 1) {
        case 3:
        case "11":
            print NR - 1
            break

        case /2[[:digit:]]+/:
            print NR

        default:
            print NR + 1

        case -1:
            print NR * -1
    }
}' /etc/passwdcopy

awk 'BEGIN {
    for (i = 0; i < 10; i++)
        print "i=" i;
}'copy

awk 'BEGIN {
    for (i = 1; i <= 100; i *= 2)
        print i
}'copy

awk 'BEGIN {
    assoc["key1"] = "val1"
    assoc["key2"] = "val2"
    for (key in assoc)
        print assoc[key];
}'copy

awk 'BEGIN {
    for (argnum in ARGV)
        print ARGV[argnum];
}' a b ccopy

awk -F: '{ x[NR] = $0 }
    END {
        for (i = NR; i > 0; i--)
        print x[i]
    }
' /etc/passwdcopy

awk -F: '{
    for (i = NF; i > 0; i--)
        printf("%s ",$i);
    print ""
}' /etc/passwdcopy

awk -F: '{
    s=0;
    for (i = 1; i <= NF; i++)
        s += $i;
    print s
}' /etc/passwdcopy

awk -F: '
    {for (i = 1; i <= NF; i++)
        s += $i;
    };
    END{print s}
' /etc/passwdcopy

awk 'BEGIN {
    while (a < 10) {
        print "- " " concatenation: " a
        a++;
    }
}'copy

awk '{
    i = 1
    do {
        print $0
        i++
    } while (i <= 5)
}' /etc/passwdcopy

awk 'BEGIN {
    break_num = 5
    for (i = 0; i < 10; i++) {
        print i
        if (i == break_num)
            break
    }
}'copy

awk 'BEGIN {
    for (x = 0; x <= 10; x++) {
        if (x == 5 || x == 6)
            continue
        printf "%d ", x
    }
    print ""
}'copy

awk 'BEGIN{printf "|%10s|\n", "hello"}'

|     hello|copy

awk 'BEGIN{printf "|%-10s|\n", "hello"}'

|hello     |copy

awk -F: '{
    printf "%-10s %s\n", $1, $(NF-1)
}' /etc/passwd | head -n 3copy

root       /root
bin        /bin
daemon     /sbincopy

awk -F: 'BEGIN {
    printf "%-10s %s\n", "User", "Home"
    printf "%-10s %s\n", "----","----"}
    { printf "%-10s %s\n", $1, $(NF-1) }
' /etc/passwd | head -n 5copy

User       Home
----       ----
root       /root
bin        /bin
daemon     /sbincopy

$ cat demo.awk
#!/usr/bin/awk -f
BEGIN { x = 23 }
      { x += 2 }
END   { print x }
$ awk -f demo.awk /etc/passwd
69copy

#!/bin/bash --noprofile --norc
export MY_VARIABLE="value"
echo "Current PATH: $PATH"copy

chsh -s /path/to/shellcopy

chsh -s $(which zsh)copy

sed -i "[range]s/[patern]/[replacement]/[options]" file_*
sed -i "2,5s|[patern]|[replacement]|[options]" file_*copy

$ sed -n '/hello/p' file.txtcopy

$ sed -n '/hello/Ip' file.txtcopy

$ sed [options] command [input-file]copy

$ cat report.txt | sed 's/Nick/John/g'copy

$ echo '123abc' | sed 's/[0-9]+//g'copy

$ echo "hello world" | sed -e 's/h/H/g' -e 's/w/W/g'
Hello Worldcopy

$ echo 's/h/H/g' >> hello.sed
$ echo 's/w/W/g' >> hello.sed
$ echo "hello world" | sed -f hello.sed
Hello Worldcopy

$ sed 's/old/new/g' file.txt
$ sed 's/old/new/g' file.txt > new.txt
$ sed 's/old/new/g' -i file.txt
$ sed 's/old/new/g' -i.backup file.txtcopy

$ sed [options] command [input-file]copy

$ cat report.txt | sed 's/Nick/John/g'copy

$ echo '123abc' | sed 's/[0-9]+//g'copy

$ echo "hello world" | sed -e 's/h/H/g' -e 's/w/W/g'
Hello Worldcopy

$ echo 's/h/H/g' >> hello.sed
$ echo 's/w/W/g' >> hello.sed
$ echo "hello world" | sed -f hello.sed
Hello Worldcopy

$ sed 's/old/new/g' file.txt
$ sed 's/old/new/g' file.txt > new.txt
$ sed 's/old/new/g' -i file.txt
$ sed 's/old/new/g' -i.backup file.txtcopy

$ sed 's/old/new/[flags]' [input-file]copy

$ sed 's/old/new/g' file.txtcopy

$ sed 's/old/new/2' file.txtcopy

$ sed '5 s/old/new/' file.txtcopy

$ sed '/hello/s/world/universe/' file.txtcopy

$ sed 's/\\$//' file.txtcopy

$ sed 's/^\s*//' file.txtcopy

$ sed 's/#.*$//' file.txtcopy

$ sed -n '/hello/p' file.txtcopy

$ sed -n '/hello/Ip' file.txtcopy

$ sed -n '/hello/!p' file.txtcopy

$ sed '2a Text after line 2' file.txtcopy

$ sed '$a THE END!' file.txtcopy

$ sed '3~3a Some text' file.txtcopy

$ sed = file.txt | sed 'N;s/\n/\t/'copy

$ sed = file.txt | sed 'N; s/^/   /; s/ *\(.\{6,\}\)\n/\1  /'copy

$ sed '/./=' file.txt | sed '/./N; s/\n/ /'copy

$ sed -n '$='copy

$ sed '5i line number five' file.txtcopy

$ sed '/hello/i Example: ' file.txtcopy

$ sed '5,7d' file.txtcopy

$ sed '3~2d' file.txtcopy

$ sed '$d' file.txtcopy

$ sed '/^Hello/d' file.txtcopy

$ sed '/^$/d' file.txtcopy

$ sed '/^#/d' file.txtcopy

$ sed Gcopy

$ sed '/^$/d;G'copy

$ sed 'G;G'copy

$ sed 'n;d'copy

$ sed '/regex/{x;p;x;}'copy

$ sed '/regex/G'copy

$ sed '/regex/{x;p;x;G;}'copy

$ sed 's/old/new/g' file.txtcopy

$ sed 's/old/new/2' file.txtcopy

$ sed '5 s/old/new/' file.txtcopy

$ sed '/hello/s/world/universe/' file.txtcopy

$ sed 's/\\$//' file.txtcopy

$ sed 's/^\s*//' file.txtcopy

$ sed 's/#.*$//' file.txtcopy

$ sed -n '/hello/p' file.txtcopy

$ sed -n '/hello/Ip' file.txtcopy

$ sed -n '/hello/!p' file.txtcopy

$ sed '2a Text after line 2' file.txtcopy

$ sed '$a THE END!' file.txtcopy

$ sed '3~3a Some text' file.txtcopy

$ sed = file.txt | sed 'N;s/\n/\t/'copy

$ sed = file.txt | sed 'N; s/^/   /; s/ *\(.\{6,\}\)\n/\1  /'copy

$ sed '/./=' file.txt | sed '/./N; s/\n/ /'copy

$ sed -n '$='copy

$ sed '5i line number five' file.txtcopy

$ sed '/hello/i Example: ' file.txtcopy

$ sed '5,7d' file.txtcopy

$ sed '3~2d' file.txtcopy

$ sed '$d' file.txtcopy

$ sed '/^Hello/d' file.txtcopy

$ sed '/^$/d' file.txtcopy

$ sed '/^#/d' file.txtcopy

$ sed Gcopy

$ sed '/^$/d;G'copy

$ sed 'G;G'copy

$ sed 'n;d'copy

$ sed '/regex/{x;p;x;}'copy

$ sed '/regex/G'copy

$ sed '/regex/{x;p;x;G;}'copy

#!/bin/shcopy

#!/bin/bashcopy

:<<EOF
注释内容...
注释内容...
注释内容...
EOFcopy

: <<'COMMENT'
这是注释的部分。
可以有多行内容。
COMMENT

:<< '
注释内容...
注释内容...
注释内容...
'

:<<!
注释内容...
注释内容...
注释内容...
!copy

#!/bin/bash
# A simple variable example
greeting=Hello
name=Tux
echo $greeting $namecopy

my_string='Hello, World!my_string="Hello, World!"copy

RUNOOB="www.runoob.com"
LD_LIBRARY_PATH="/bin/"
_var="123"
var2="abc"copy

for file in \` ls / etc \`
for file in $ (ls / etc)copy

my_array=(1 2 3 4 5)copy

#!/bin/bash

myUrl="https://www.google.com"
readonly myUrl
myUrl="https://www.runoob.com"copy

unset variable_namecopy

my_string='Hello, World!'
my_string="Hello, World!"copy

your\_name = "runoob"
\# 使用双引号拼接
greeting = "hello, " $your\_name "!"
greeting\_1 = "hello, ${your\_name}!"
echo $greeting $greeting\_1

\# 使用单引号拼接
greeting\_2 = 'hello, ' $your\_name '!'
greeting\_3 = 'hello, ${your\_name}!'
echo $greeting\_2 $greeting\_3copy

hello, runoob ! hello, runoob !
hello, runoob ! hello, ${your_name} !copy

string = "abcd"
echo ${#string} \# 输出 4copy

数组名=(值1 值2 ... 值n)copy

array_name=(value0 value1 value2 value3)copy

array_name=(
value0
value1
value2
value3
)copy

array_name[0]=value0
array_name[1]=value1
array_name[n]=valuencopy

${数组名[下标]}copy

valuen=${array_name[n]}copy

echo ${array_name[@]}copy

\# 取得数组元素的个数
length = ${#array\_name\[@\]}
\# 或者
length = ${#array\_name\[\*\]}
\# 取得数组单个元素的长度
length = ${#array\_name\[n\]}copy

#!/bin/bash

for arg in "$*"; do
    echo "****:" $arg
done
echo --------------
for arg in "$@"; do
    echo "@@@@:" $arg
donecopy

$ ./testparams.sh This is a test
****: This is a test
--------------
@@@@: This
@@@@: is
@@@@: a
@@@@: testcopy

# ls {ex1,ex2}.sh
ex1.sh  ex2.sh
# ls {ex{1..3},ex4}.sh
ex1.sh  ex2.sh  ex3.sh  ex4.sh
# ls {ex[1-3],ex4}.sh
ex1.sh  ex2.sh  ex3.sh  ex4.shcopy

${var:-string}
${var:+string}
${var:=string}
${var:?string}copy

default_name="Guest"
unset name  # 确保 name 未定义

# 如果 name 为空，则使用 default_name 的值
echo "Hello, ${name:-$default_name}"  # 输出: Hello, Guestcopy

# 是去掉左边(在键盘上#在$之左边)
% 是去掉右边(在键盘上%在$之右边)copy

${var%pattern}
${var%%pattern
${var#pattern}
${var##pattern}copy

# var=testcase
# echo $var
testcase
# echo ${var%s*e}
testca
# echo $var
testcase
# echo ${var%%s*e}
te
# echo ${var#?e}
stcase
# echo ${var##?e}
stcase
# echo ${var##*e}

# echo ${var##*s}
e
# echo ${var##test}
casecopy

${var:num}
${var:num1:num2}
${var/pattern/pattern}
${var//pattern/pattern}copy

[root@centos ~]# var=/home/centos
[root@centos ~]# echo $var
/home/centos
[root@centos ~]# echo ${var:5}
/centos
[root@centos ~]# echo ${var: -6}
centos
[root@centos ~]# echo ${var:(-6)}
centos
[root@centos ~]# echo ${var:1:4}
home
[root@centos ~]# echo ${var/o/h}
/hhme/centos
[root@centos ~]# echo ${var//o/h}
/hhme/centhscopy

type [

[ is a shell builtincopy

if ($i<5)
if [ $i -lt 5 ]
if [ $a -ne 1 -a $a != 2 ]
if [ $a -ne 1] && [ $a != 2 ]
if [[ $a != 1 && $a != 2 ]]

for i in $(seq 0 4);do echo $i;done
for i in \`seq 0 4\`;do echo $i;done
for ((i=0;i<5;i++));do echo $i;done
for i in {0..4};do echo $i;donecopy

[[ "hello" =~ ^h ]]   # 正则匹配（返回 true）copy

# [ ] 必须加引号
[ "$name" = "Alice" ] && echo "Hello Alice"

# [[ ]] 更灵活
[[ $name == A* ]] && echo "Name starts with A"copy

# [ ] 和 [[ ]] 均可，但后者更安全
[ -f "/path/$file" ] && echo "File exists"
[[ -f /path/$file ]] && echo "File exists"copy

# [ ] 用 -a/-o
[ "$age" -gt 18 -a "$age" -lt 60 ] && echo "Valid age"

# [[ ]] 用 &&/||
[[ $age -gt 18 && $age -lt 60 ]] && echo "Valid age"copy

var=$((expression))copy

#!/bin/bash

var=\`df -h | grep tmpfs\`
echo $varcopy

repo=~"/projects/repo1"  # 或直接写 ~/projects/repo1（不加引号）
cd "$repo"               # 此时 $repo 已是展开后的绝对路径copy

#!/bin/bash

# 显式展开家目录
HOME_DIR=$(eval echo "~")  # 或直接写 HOME_DIR="$HOME"

repos=(
    "$HOME_DIR/projects/repo1"
    "$HOME_DIR/work/repo2"
)copy

name="Alice"

echo "Hello, $name"   # 输出: Hello, Alice
echo 'Hello, $name'   # 输出: Hello, $namecopy

echo "Today is $(date)"  # 输出: Today is Mon Jul 1 12:00:00 UTC 2024
echo 'Today is $(date)'  # 输出: Today is $(date)copy

echo "Path is \$HOME"    # 输出: Path is $HOME（\$ 被转义）
echo 'Path is \$HOME'    # 输出: Path is \$HOME（完全字面）copy

echo "She said: 'Hello!'"   # 输出: She said: 'Hello!'
echo 'He said: "Hi!"'       # 输出: He said: "Hi!"copy

alias rm='rm -i'          # 单引号内定义别名（避免变量提前展开）
echo "It's a sunny day."  # 双引号内嵌套单引号（无需转义）copy

echo "Line 1\nLine 2"     # 输出: Line 1\nLine 2（\n 未被转义为换行）
echo -e "Line 1\nLine 2"  # 输出两行（-e 启用转义）
echo 'Line 1\nLine 2'     # 输出: Line 1\nLine 2（完全字面）copy

echo "input a"
read a
echo "input b"
read b

read -n 3 -t 5 -s -p "input 3 charater, wait for 5 seconds, silent" c
echo "$c"

printf "a=%s,b=%s,sum is %s" $a $b $((a + b))copy

#!/bin/bash

for x in $@
do
    echo "Entered arg is $x"
donecopy

#!/bin/bash

LINE=1

while read -r CURRENT_LINE
    do
        echo "$LINE: $CURRENT_LINE"
    ((LINE++))
done < "sample_file.txt"copy

# 将标准错误重定向到文件描述符3，再重定向到文件
exec 3>&1  # 备份标准输出到3
cmd 2>&1 >output.log | tee -a error.log  # 错误流单独处理
exec 1>&3  # 恢复标准输出copy

# 静默执行命令（忽略所有输出）
cmd > /dev/null 2>&1copy

# 将 file.txt 的内容作为 wc 命令的输入
wc -l < file.txtcopy

command << DELIMITER
多行文本...
DELIMITERcopy

# 将多行文本传递给 cat 命令
cat << EOF
第一行
第二行
变量值: $HOME
EOFcopy

第一行
第二行
变量值: /home/usernamecopy

# 将字符串传递给 grep 命令
grep "hello" <<< "hello world"copy

# 从配置文件读取输入
while read line; do
    echo "配置行: $line"
done < config.txtcopy

# 生成多行配置文件
cat > app.conf << EOF
server_ip=192.168.1.1
port=8080
EOFcopy

# 快速检查字符串是否包含子串
grep "error" <<< "$log_content"copy

# 从input.txt读取，结果写入output.txt
command < input.txt > output.txtcopy

# 标准输出到out.log，错误到err.log
command > out.log 2> err.logcopy

# 方式1（推荐）
command &> combined.log

# 方式2（传统写法）
command > combined.log 2>&1copy

# 比较两个目录的文件列表差异
diff <(ls /path/to/dir1) <(ls /path/to/dir2)

# 将输出同时写入文件和压缩
echo "data" | tee >(gzip > output.gz) > original.txtcopy

#!/bin/bash
exec 3>&1  # 备份标准输出到描述符3
exec > >(tee -a stdout.log) 2> >(tee -a stderr.log >&2)  # 分离输出和错误

echo "正常消息"  # 写入stdout.log
ls /nonexistent  # 错误写入stderr.log

exec 1>&3  # 恢复标准输出
echo "回到终端显示"copy

{
    echo "标准输出1"
    echo "标准错误1" >&2
    echo "标准输出2"
    echo "标准错误2" >&2
} > >(grep "标准输出" > out.txt) 2> >(grep "标准错误" > err.txt)copy

if [ ... ]
then
  # if-code
else
  # else-code
ficopy

if [ ... ] ; then
  # if-code
else
  # else-code
ficopy

#!/bin/sh
if [ "$X" -lt "0" ]
then
  echo "X is less than zero"
fi
if [ "$X" -gt "0" ]; then
  echo "X is more than zero"
fi
[ "$X" -le "0" ] && \
      echo "X is less than or equal to  zero"
[ "$X" -ge "0" ] && \
      echo "X is more than or equal to zero"
[ "$X" = "0" ] && \
      echo "X is the string or number \"0\""
[ "$X" = "hello" ] && \
      echo "X matches the string \"hello\""
[ "$X" != "hello" ] && \
      echo "X is not the string \"hello\""
[ -n "$X" ] && \
      echo "X is of nonzero length"
[ -f "$X" ] && \
      echo "X is the path of a real file" || \
      echo "No such file: $X"
[ -x "$X" ] && \
      echo "X is the path of an executable file"
[ "$X" -nt "/etc/passwd" ] && \
      echo "X is a file which is newer than /etc/passwd"


read a
read b
read c

if [ $a == $b -a $b == $c -a $a == $c ] # -a means
then
echo EQUILATERAL

elif [ $a == $b -o $b == $c -o $a == $c ] # -o means or
then
echo ISOSCELES
else
echo SCALENE

ficopy

for i in {1..5}
do
    echo $i
done

for X in cyan magenta yellow
do
    echo $X
donecopy

i=1
while [[ $i -le 10 ]] ; do
   echo "$i"
  (( i += 1 ))
donecopy

# 定义数组（空格分隔元素，可含特殊字符）
fruits=("Apple" "Banana" "Orange" "Grape" "Watermelon")
for fruit in "${fruits[@]}"; do
    echo "Fruit: $fruit"
done
for i in "${!fruits[@]}"; do
    echo "Index $i: ${fruits[i]}"
donecopy

# 定义仓库目录列表（支持绝对路径或相对路径）
repos=(
    "/path/to/repo1"
    "/path/to/repo2"
    "/path/to/repo3"
    "/path/to/repo4"
)

# 遍历所有仓库
for i in "${repos[@]}"; do
    echo "Updating repo: $i"
    cd "$i" || { echo "Failed to enter $i"; continue; }

    # 执行 git pull
    git pull origin main  # 假设分支是 main，根据实际情况修改

    # 检查 git pull 是否成功
    if [ $? -eq 0 ]; then
        echo "Successfully updated: $i"
    else
        echo "Failed to update: $i"
    fi

    echo "----------------------------------"
done

echo "All repositories updated!"copy

#!/bin/sh
docs="Usage: \
\n\tbash $0 [options] \
\nOptions: \
\n\t-N NAME: your name, required\
\n\t-a AGE: your age, required\
\n\t-v: verbose mode, optional\
\nExample: \
\n\t bash $0 -N balabala -a 24 "

usage() {
    echo -e $docs >&2
    exit 1
}

if [ $# -eq 0 ] || [ $1 == -h ]; then usage; fi

## 设置变量的默认值
verbose=n

## 检查变量参数是否缺失
check() {
    opt=$1
    arg=$2

    if [[ $arg =~ ^- ]] || [ ! $arg ]
    then
        echo "ERROR: -$opt expects an corresponding argument" >&2
        usage
    fi
}

## 循环解析脚本的所有positional parameters
while getopts :vN:a: opt
do
    case $opt in
    v)
        verbose=y
        ;;
    N)
        check N $OPTARG
        name=$OPTARG
        ;;
    a)
        check a $OPTARG
        age=$OPTARG
        ;;
    :)
        echo "ERROR: -$OPTARG expects an corresponding argument" >&2
        usage
        ;;
    \?) # shell里'?'具有匹配一位任意字符的作用，因此需要转义为普通字符
        echo "ERROR: unkown option -$OPTARG" >&2
        usage
        ;;
    esac
done

## 如果用户没有提供-N选项
if [ ! $name ]
then
    echo ERROR: option -N is required >&2
    usage
fi

## 如果用户没有提供-a选项
if [ ! $age ]
then
    echo ERROR: option -a is required >&2
    usage
fi

if [ $verbose == n ]
then
    echo "Merry Christmas! $name"
else
    echo "Hello, your name is $name, you are $age years old!"
    echo "Merry Christmas!!"
ficopy

# Cron job example
* * * * * sh /path/to/script.shcopy