Corresponds to the OS. System (CMD) Return Value in Python and the return value of Linux commands

I. Relationship between the return value of OS. System (CMD) in Python and the return value of Linux commands (For details, refer to the additional content in this article)

Everyone is used to using the OS. systemv () function to execute Linux commands. the return value of this function is in decimal number (corresponding to a 16-bit binary number ). The Conversion Relationship Between the return value of the function and the return value of the Linux Command is as follows: the return value (decimal) of the function is converted to 16 binary numbers, intercept the high eight bits (if the low bits are 0, there are 131 error codes related to the operating system, so the low bits are all zero ), the return value is 0 in decimal number.

For example:

OS. System () returns 0. the return value of the Linux Command is also 0.

OS. System () the return value is 256, and The hexadecimal binary number is:, and the high octal decimal number is 1. corresponding to the Linux Command, the return value is 1.

OS. System () return value is 512, And the hexadecimal binary number is:, and the high octal decimal number is 2. corresponding to the Linux Command return value 2

...... Others

OS. System () returns 32512, And the hexadecimal binary number is: 0111111111,00000000. The high octal transpose multiplication decimal value is 127, corresponding to the Linux Command return value 127.

........

To put it simply, the return code of the Linux Command shifts eight places to the left, and then converts it to decimal to the return value of the OS. System () function.

Additional content

Linux Command Return Value

After a Linux Command is executed, whether it is successful or not, there is a return value:

If the value is 0, the command is successfully executed.

Other values indicate errors. The specific error codes are described as follows:

 "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"