shell-script

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記錄板端使用到的shell script一些方式

shell script

如何執行目錄內所有script (run-parts)

  • 使用run-parts可以參數給shell script
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run-parts /etc/ppp/ip-down.d \
  --arg="$1" --arg="$2" --arg="$3" --arg="$4" --arg="$5" --arg="$6"
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# follow any symlink to find the real file
REALRESOLVCONF=$(readlink -f /etc/resolv.conf)

檢查檔案是否在存，若不存在則離開script

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# If pppconfig has been removed we are not supposed to do anything.
test -f /usr/sbin/pppconfig || exit 0

測試變數是否為空，若是則離開script

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# If we don't have a provider we have nothing to do.
test -z "$PPP_IPPARAM" && exit 0

busybox command

run-parts 說明

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BusyBox v1.16.1 (2016-02-19 09:03:37 UTC) multi-call binary.

Usage: run-parts [-t] [-l] [-a ARG] [-u MASK] DIRECTORY

Run a bunch of scripts in DIRECTORY

Options:
        -t      Print what would be run, but don't actually run anything
        -a ARG  Pass ARG as argument for every program
        -u MASK Set the umask to MASK before running every program
        -l      Print names of all matching files even if they are not executable
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Usage: readlink [-fnv] FILE

Display the value of a symlink

Options:
        -f      Canonicalize by following all symlinks
        -n      Don't add newline
        -v      Verbose

shell test 用法

  • -x
    • True if file exists and is executable
    • [ -x .] : 成功回傳0，其它則為非0
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DAEMON=/usr/sbin/ez-ipupdate
NAME=ez-ipupdate

[ -x $DAEMON ] || exit 0
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test expression

 [ expression ]
        The test utility evaluates the expression and, if it evaluates to true, returns a zero (true) exit status; otherwise it returns 1 (false).  If there is no expression,
        test also returns 1 (false).

        All operators and flags are separate arguments to the test utility.

        The following primaries are used to construct expression:

        -b file       True if file exists and is a block special file.

        -c file       True if file exists and is a character special file.

        -d file       True if file exists and is a directory.

        -e file       True if file exists (regardless of type).

        -f file       True if file exists and is a regular file.

        -g file       True if file exists and its set group ID flag is set.

        -h file       True if file exists and is a symbolic link.

        -k file       True if file exists and its sticky bit is set.

        -n string     True if the length of string is nonzero.

        -p file       True if file is a named pipe (FIFO).

        -r file       True if file exists and is readable.

        -s file       True if file exists and has a size greater than zero.

        -t file_descriptor
                      True if the file whose file descriptor number is file_descriptor is open and is associated with a terminal.

        -u file       True if file exists and its set user ID flag is set.

        -w file       True if file exists and is writable.  True indicates only that the write flag is on.  The file is not writable on a read-only file system even if this
                      test indicates true.

        -x file       True if file exists and is executable.  True indicates only that the execute flag is on.  If file is a directory, true indicates that file can be
                      searched.

        -z string     True if the length of string is zero.

        -L file       True if file exists and is a symbolic link.  This operator is retained for compatibility with previous versions of this program.  Do not rely on its exis‐
                      tence; use -h instead.

        -O file       True if file exists and its owner matches the effective user id of this process.

        -G file       True if file exists and its group matches the effective group id of this process.

        -S file       True if file exists and is a socket.

        file1 -nt file2
                      True if file1 and file2 exist and file1 is newer than file2.

        file1 -ot file2
                      True if file1 and file2 exist and file1 is older than file2.

        file1 -ef file2
                      True if file1 and file2 exist and refer to the same file.

        string        True if string is not the null string.

        s1 = s2       True if the strings s1 and s2 are identical.

        s1 != s2      True if the strings s1 and s2 are not identical.

        s1 < s2       True if string s1 comes before s2 based on the ASCII value of their characters.

        s1 > s2       True if string s1 comes after s2 based on the ASCII value of their characters.

        n1 -eq n2     True if the integers n1 and n2 are algebraically equal.

        n1 -ne n2     True if the integers n1 and n2 are not algebraically equal.

        n1 -gt n2     True if the integer n1 is algebraically greater than the integer n2.

        n1 -ge n2     True if the integer n1 is algebraically greater than or equal to the integer n2.

        n1 -lt n2     True if the integer n1 is algebraically less than the integer n2.

        n1 -le n2     True if the integer n1 is algebraically less than or equal to the integer n2.

        These primaries can be combined with the following operators:

        ! expression  True if expression is false.

        expression1 -a expression2
                      True if both expression1 and expression2 are true.

        expression1 -o expression2
                      True if either expression1 or expression2 are true.

        (expression)  True if expression is true.

        The -a operator has higher precedence than the -o operator.

busybox config

目前embedded是以ash為主，但也新增相容bash部分

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    Choose your default shell (ash)  ---> 
--- ash
[*]   bash-compatible extensions 
[*]   Job control
[*]   alias support 
[*]   Builtin getopt to parse positional parameters
[*]   Builtin version of 'echo'
[*]   Builtin version of 'printf'   
[*]   Builtin version of 'test' 
[*]   'command' command to override shell builtins 
[ ]   Check for new mail on interactive shells  
[*]   Optimize for size instead of speed
[*]   Pseudorandom generator and $RANDOM variable 
[*]   Expand prompt str

其它

如何取得script自已的pid

  • 使用$$取得pid

  • t1.sh

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    #!/bin/bash


    echo $$
    for((i=0; i<11; i=i+1))
    do
        echo $i
        sleep 1
    done

  • [root@localhost tt]# ./t1.sh 

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    18154
    0
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  • check
    t1.sh pid為18154

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    root     18154 18056  0 11:54 pts/2    00:00:00 /bin/bash ./t1.sh
    root     18158 18154  0 11:54 pts/2    00:00:00 sleep 1
    root     18159 16537  0 11:54 pts/1    00:00:00 ps -ef