Shell指令碼中$0、$?、$!、$$、$*、$#、$@等的意義以及linux命令執行返回值意義

(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、$2是第2引數…。 1.2、指令碼舉例 我們先寫一個簡單的指令碼，執行以後再解釋各個變數的意義 # touch variable # vi variable 指令碼內容如下： #!/bin/sh echo "number:$#" 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}"

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