Shell指令碼中$0、$?、$!、$$、$*、$#、$@等的意義以及linux命令執行返回值代表意義
阿新 • • 發佈:2020-08-13
Shell指令碼中$0、$?、$!、$$、$*、$#、$@等的意義以及linux命令執行返回值意義
我們先寫一個簡單的指令碼,執行以後再解釋各個變數的意義
# touch variable
# vi variable
指令碼內容如下:
#!/bin/sh
echo "number:$#"
echo "scname:$0"
echo "first :$1"
echo "second:$2"
echo "argume:$@"
儲存退出
賦予指令碼執行許可權
# chmod +x variable
執行指令碼
# ./variable aa bb
number:2
scname:./variable
first: aa
second:bb
argume:aa bb
結果分析
通過顯示結果可以看到:
$# 是傳給指令碼的引數個數
$0 是指令碼本身的名字
$1是傳遞給該shell指令碼的第一個引數
$2是傳遞給該shell指令碼的第二個引數
$@ 是傳給指令碼的所有引數的列表
(2) linux命令執行返回值說明
在 Linux 下,不管你是啟動一個桌面程式也好,還是在控制檯下執行命令,所有的程式在結束時,都會返回一個數字值,這個值叫做返回值,或者稱為錯誤號 ( Error Number )。
2.1、在控制檯下,有一個特殊的環境變數$?,儲存著前一個程式的返回值,我們可以試試:
$ ls *.png
Diagram1.pngeqn.pngpeazip.png
eqn4.pngMandelbrot.pngx2.png
$echo $?
0
先隨便執行個命令,比如像上面的 ls 某些檔案,然後通過 echo $?,列印 $? 的值~
我們發現返回值是 0,這是什麼意思呢?
只要返回值是 0,就代表程式執行成功了~
也就是說,如果 $? 變數的值不是 0 的話,就表示上一個命令在執行的過程中出錯了。
2.2、我們可以試著 ls 一個不存在的檔案:
$ ls linuxgem
ls: 無法訪問 linuxgem: 沒有那個檔案或目錄
$ echo $?
2
這樣,對於某些打印出一堆不熟悉的英文資訊的命令,可以方便的看出它是否成功執行結束。
不過,每次都 echo $? 一下太累了,沒關係,你可以把 $? 放在提示符裡去:
2.3、將上次命令執行是否成功的返回值放到提示符裡面去:export PS1="[\$?]${PS1}"
(1) Shell指令碼中$0、$?、$!、$$、$*、$#、$@等的意義說明
1.1、簡要說明 ps: 你在Linux環境下多試下就明白了 $$ Shell本身的PID(ProcessID,即指令碼執行的當前程序ID號) $! Shell最後執行的後臺Process的PID(後臺執行的最後一個程序的程序ID號) $? 最後執行的命令的結束程式碼(返回值)即執行上一個指令的返回值 (顯示最後命令的退出狀態。0表示沒有錯誤,其他任何值表明有錯誤) $- 顯示shell使用的當前選項,與set命令功能相同 $* 所有引數列表。如"$*"用「"」括起來的情況、以"$1 $2 … $n"的形式輸出所有引數,此選項引數可超過9個。 $@ 所有引數列表。如"$@"用「"」括起來的情況、以"$1" "$2" … "$n" 的形式輸出所有引數。 $@ 跟$*類似,但是可以當作陣列用 $# 新增到Shell的引數個數 $0 Shell本身的檔名 $1~$n 新增到Shell的各引數值。$1是第1引數、$2是第2引數…。 1.2、指令碼舉例tom@localhost ~ $ export PS1="[\$?]${PS1}" [0]tom@localhost ~ $export PS1="[\$?]${PS1}"這個命令把 $? 的值放在的提示符的最前面,這樣每次執行完命令,這個值都會自動更新,這下就一目瞭然了~ 2.3、用perror檢視錯誤提示 那麼如果返回的值不是 0,我們要怎麼知道是那裡出錯了呢? 大多數的程式出錯都會給出提示,如果沒有提示的話,可以用perror這個程式來檢視錯誤的資訊,比如返回值是 2,我們可以執行: $ perror 2 OS error code2:No such file or directory 這樣就清楚了,原來是檔案不存在~ 2.4、給出錯誤程式碼及其具體原因對照表:
"OS error code 1: Operation not permitted" "OS error code 2: No such file or directory" "OS error code 3: No such process" "OS error code 4: Interrupted system call" "OS error code 5: Input/output error" "OS error code 6: No such device or address" "OS error code 7: Argument list too long" "OS error code 8: Exec format error" "OS error code 9: Bad file descriptor" "OS error code 10: No child processes" "OS error code 11: Resource temporarily unavailable" "OS error code 12: Cannot allocate memory" "OS error code 13: Permission denied" "OS error code 14: Bad address" "OS error code 15: Block device required" "OS error code 16: Device or resource busy" "OS error code 17: File exists" "OS error code 18: Invalid cross-device link" "OS error code 19: No such device" "OS error code 20: Not a directory" "OS error code 21: Is a directory" "OS error code 22: Invalid argument" "OS error code 23: Too many open files in system" "OS error code 24: Too many open files" "OS error code 25: Inappropriate ioctl for device" "OS error code 26: Text file busy" "OS error code 27: File too large" "OS error code 28: No space left on device" "OS error code 29: Illegal seek" "OS error code 30: Read-only file system" "OS error code 31: Too many links" "OS error code 32: Broken pipe" "OS error code 33: Numerical argument out of domain" "OS error code 34: Numerical result out of range" "OS error code 35: Resource deadlock avoided" "OS error code 36: File name too long" "OS error code 37: No locks available" "OS error code 38: Function not implemented" "OS error code 39: Directory not empty" "OS error code 40: Too many levels of symbolic links" "OS error code 42: No message of desired type" "OS error code 43: Identifier removed" "OS error code 44: Channel number out of range" "OS error code 45: Level 2 not synchronized" "OS error code 46: Level 3 halted" "OS error code 47: Level 3 reset" "OS error code 48: Link number out of range" "OS error code 49: Protocol driver not attached" "OS error code 50: No CSI structure available" "OS error code 51: Level 2 halted" "OS error code 52: Invalid exchange" "OS error code 53: Invalid request descriptor" "OS error code 54: Exchange full" "OS error code 55: No anode" "OS error code 56: Invalid request code" "OS error code 57: Invalid slot" "OS error code 59: Bad font file format" "OS error code 60: Device not a stream" "OS error code 61: No data available" "OS error code 62: Timer expired" "OS error code 63: Out of streams resources" "OS error code 64: Machine is not on the network" "OS error code 65: Package not installed" "OS error code 66: Object is remote" "OS error code 67: Link has been severed" "OS error code 68: Advertise error" "OS error code 69: Srmount error" "OS error code 70: Communication error on send" "OS error code 71: Protocol error" "OS error code 72: Multihop attempted" "OS error code 73: RFS specific error" "OS error code 74: Bad message" "OS error code 75: Value too large for defined data type" "OS error code 76: Name not unique on network" "OS error code 77: File descriptor in bad state" "OS error code 78: Remote address changed" "OS error code 79: Can not access a needed shared library" "OS error code 80: Accessing a corrupted shared library" "OS error code 81: .lib section in a.out corrupted" "OS error code 82: Attempting to link in too many shared libraries" "OS error code 83: Cannot exec a shared library directly" "OS error code 84: Invalid or incomplete multibyte or wide character" "OS error code 85: Interrupted system call should be restarted" "OS error code 86: Streams pipe error" "OS error code 87: Too many users" "OS error code 88: Socket operation on non-socket" "OS error code 89: Destination address required" "OS error code 90: Message too long" "OS error code 91: Protocol wrong type for socket" "OS error code 92: Protocol not available" "OS error code 93: Protocol not supported" "OS error code 94: Socket type not supported" "OS error code 95: Operation not supported" "OS error code 96: Protocol family not supported" "OS error code 97: Address family not supported by protocol" "OS error code 98: Address already in use" "OS error code 99: Cannot assign requested address" "OS error code 100: Network is down" "OS error code 101: Network is unreachable" "OS error code 102: Network dropped connection on reset" "OS error code 103: Software caused connection abort" "OS error code 104: Connection reset by peer" "OS error code 105: No buffer space available" "OS error code 106: Transport endpoint is already connected" "OS error code 107: Transport endpoint is not connected" "OS error code 108: Cannot send after transport endpoint shutdown" "OS error code 109: Too many references: cannot splice" "OS error code 110: Connection timed out" "OS error code 111: Connection refused" "OS error code 112: Host is down" "OS error code 113: No route to host" "OS error code 114: Operation already in progress" "OS error code 115: Operation now in progress" "OS error code 116: Stale NFS file handle" "OS error code 117: Structure needs cleaning" "OS error code 118: Not a XENIX named type file" "OS error code 119: No XENIX semaphores available" "OS error code 120: Is a named type file" "OS error code 121: Remote I/O error" "OS error code 122: Disk quota exceeded" "OS error code 123: No medium found" "OS error code 124: Wrong medium type" "OS error code 125: Operation canceled" "OS error code 126: Required key not available" "OS error code 127: Key has expired" "OS error code 128: Key has been revoked" "OS error code 129: Key was rejected by service" "OS error code 130: Owner died" "OS error code 131: State not recoverable" "MySQL error code 132: Old database file" "MySQL error code 133: No record read before update" "MySQL error code 134: Record was already deleted (or record file crashed)" "MySQL error code 135: No more room in record file" "MySQL error code 136: No more room in index file" "MySQL error code 137: No more records (read after end of file)" "MySQL error code 138: Unsupported extension used for table" "MySQL error code 139: Too big row" "MySQL error code 140: Wrong create options" "MySQL error code 141: Duplicate unique key or constraint on write or update" "MySQL error code 142: Unknown character set used" "MySQL error code 143: Conflicting table definitions in sub-tables of MERGE table" "MySQL error code 144: Table is crashed and last repair failed" "MySQL error code 145: Table was marked as crashed and should be repaired" "MySQL error code 146: Lock timed out; Retry transaction" "MySQL error code 147: Lock table is full; Restart program with a larger locktable" "MySQL error code 148: Updates are not allowed under a read only transactions" "MySQL error code 149: Lock deadlock; Retry transaction" "MySQL error code 150: Foreign key constraint is incorrectly formed" "MySQL error code 151: Cannot add a child row" "MySQL error code 152: Cannot delete a parent row"
參考:https://blog.csdn.net/u012359618/article/details/51442966