calmsacibis995
75 lines
2.2 KiB
Plaintext
75 lines
2.2 KiB
Plaintext
'\"macro stdmacro
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.if n .pH g3s.system @(#)system 40.15 of 5/22/91
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.\" Copyright 1991 UNIX System Laboratories, Inc.
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.\" Copyright 1989, 1990 AT&T
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.nr X
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.if \nX=0 .ds x} system 3S "C Development Set" "\&"
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.if \nX=1 .ds x} system 3S "C Development Set"
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.if \nX=2 .ds x} system 3S "" "\&"
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.if \nX=3 .ds x} system "" "" "\&"
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.TH \*(x}
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.SH NAME
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\f4system\f1 \- issue a shell command
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.SH SYNOPSIS
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\f4#include <stdlib.h>\f1
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.PP
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\f4int system (const char \(**string);\f1
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.SH DESCRIPTION
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\f4system\fP
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causes the
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.I string\^
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to be given to the shell
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[see \f4sh\fP(1)]
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as input, as if the string had been typed as a command
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at a terminal.
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The current process waits until the shell has
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completed, then returns the exit status of the shell
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in the format specified by \f4waitpid\fP(2).
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.PP
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If \f2string\f1 is a \f4NULL\fP pointer, \f4system\fP checks if \f4/sbin/sh\fP
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exists and is executable. If \f4/sbin/sh\fP is available, \f4system\fP
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returns non-zero; otherwise it returns zero.
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.PP
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\f4system\fP fails if one or more of the following are true:
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.TP 12
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\f4EAGAIN\fP
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The system-imposed limit on the total number of processes under execution by
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a single user would be exceeded.
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.TP 12
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\f4EINTR\fP
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\f4system\fP was interrupted by a signal.
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.TP 12
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\f4ENOMEM\fP
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The new process requires more memory than is allowed by the system-imposed
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maximum \f4MAXMEM\fP.
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.SH "SEE ALSO"
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\f4exec\fP(2),
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\f4waitpid\fP(2),
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\f4sh\fP(1).
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.SH DIAGNOSTICS
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\f4system\fP
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forks to create a child process
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that in turn execs
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\f4/sbin/sh\fP
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in order to execute
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.IR string .
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If the fork or exec fails,
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\f4system\fP
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returns \-1 and sets
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\f4errno\fP.
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.SH NOTES
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Calling \f4system\fP(3S) in a program that is set user ID to
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\f4root\fP is difficult to do without creating unintended
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security problems.
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For example, since \f4system\fP invokes a copy of \f4sh\fP(1)
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to execute the supplied command,
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the programmer must be extremely careful not to
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allow critical environment variables, such
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as \f4\s-1PATH\s+1\fP, which determine the behavior of the shell
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to be passed through from the environment of the invoking user
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without modification.
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It is recommended that \f4system\fP(3S) not be used by set user
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ID programs.
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.\" @(#)system.3s 6.3 of 10/20/83
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.Ee
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